Road Trip for 18-y-o with Friend?

At 18 she’s an adult ... she really doesn’t need your permission and personally I think the time for parent rules has passed. Whatever you’ve taught her has clearly worked well! The one request I think you can fairly make is, please check in once during the trip, for safety. My family is English, and it is incredibly common for 17-19 year olds to travel for MONTHS as part of their gap year, with occasional check ins and no parent imposed rules. They are adults. A 2 day trip is not a big deal.

I think this sounds like a well-thought-out trip and a nice way to celebrate the end to an unusual high school career for our recent graduates - I'd be inclined to say yes if it was my kid (I have a son the same age, but not a daughter). Make sure they research the area a little so they have some ideas of what they want to do and what areas they might want to avoid. And make the hotel reservations with them in advance - on a similar trip with some girlfriends at that age years ago, I learned the hard way that 18 wasn't old enough to make a last-minute hotel reservation (maybe that's changed now in the internet age, but it's something to consider - there may be other things they aren't yet legally old enough to do on their own). And maybe get them some kind of roadside assistance plan (I like Better World Club) if you don't have one already, to cover any towing/flat tires/etc. just in case. Have a plan with her about when and how she'll check in - a daily text once they're back in the hotel for the night or something - for your own peace of  mind. I bet they'll have a great time!

My daughter is in the same situation doing the same trip right now with 2 friends - the main risk in my view was long driving times, so she flew to Socal and has a friend down there driving around. It's the best summer of any kid's life and we're trying to let her enjoy it without too many strings. Funding depends on your situation but you're only 18 once and I'm happy to support her having a good trip.

What fun!  If she is a responsible and trustworthy young woman, I would say yes.

One thing to be aware of is, many hotels will not allow an 18 year old to check in - their minimum age is often 21.  But there are hotels that will allow it.  Best Westerns often allow 18 year olds, and the La Quinta chain generally allows it as well.  They will need to call around to confirm the individual hotel's rules.  (We run into this all the time when my daughter drives across the country to attend college).  

I hope they have a wonderful time!  

She’s 18. Your days of setting ground rules are pretty much done - especially if she’s off to college in the fall. I’d give her some money and tell her to have fun. 

Kids deserve to have their independence and we can help by making sure they know how to keep themselves safe while exploring the world. We teach theM how to swim tO be safe near water, and it’s also important to teach them “people safety” skills like how to be aware of your surroundings and those in them, how to set clear cheerful respectful boundaries, how to leave if something feels unsafe or where to go for help. I highly recommend Kidpower.org as a resource for teaching your daughter the street smart skills she can use throughout her life as she does these things independently. My son and his girlfriend took a class together before heading off to college and it really helped them!

This is kind of a classic, and seems relatively safe. The one thought I had was to consider having them take the Coast Starlight train to LA and use transit when they are there. Santa Monica has a very good bus system which they can supplement with Uber/Lyft at night. When kids run into problems on these trips it is almost always from the driving. I think it is fine for you to subsidize the trip as a graduation present, if you have the resources. 

Prior to reading others' responses about the current crime issues in Santa Monica, my biggest concern would have been a relatively new driver navigating an unfamiliar area. GPS navigation makes it easier than it used to be, but it's still harder to juggle navigation with all the other things your have to pay attention to while driving, and LA is not a particularly easy city to drive in. I saw another response was concerned about the long distance drive down to LA, but seemed blasé  about driving around LA; I'm the opposite. I find distance driving is pretty easy if you watch out for fatigue, and the girls could switch off driving. I'd be encouraging my daughter to get around mostly on foot and public transportation and to minimize driving around her destination city. That presuming a relative level of safety in the destination city--hopefully she and her friend can find a destination that satisfies their goals and is safer.

I would say yes, but go over various emergencies, so if one comes up she knows what to do. What if the car breaks down, what if there is a hotel fire, what if her purse gets stolen. Emergencies will eventually come up, we just need to know how to deal with them. 

To everyone saying 18 is an adult... the science actually says that your brain hasn't entered adulthood until 25.

The prefrontal cortex is the part of the brain that handles rational thought and judgment. This part of the brain isn't fully developed until 25. One of many sources

So 18 being the point of adulthood/maturity is purely a legal (and not a biological) construct. Just FYI.

In theory I would say yes, this sounds ok for an 18 yo to travel with a friend. My biggest concern, though, would be the driving - both going there on the highways and in and around LA. There are so any reckless, rude, impatient drivers who are not paying attention. The last time I visited LA (3 or 4 years ago) I was shocked at how aggressive the drivers are now compared to when I was growing up there in the 1980s. I think an 18 yo still does not have the driving experience required for such a trip. Flying to a big city like Manhattan where no car is needed sounds like a safer option IMO.