I can't say I fully relate as I knew where I was going to go after high school by the time I graduated but from what you've said it seems like the best option by far is to try to figure out a way to get your license and a way to drive yourself. It might seem intimidating but you know, it's probably better than the alternative, and you kinda have to learn eventually anyway so why not start now?
In any case, I remember the days of waiting around on my dad (who went to school, then worked) or trying to get rides off other people and let me tell you, I do not miss them. The ability to choose when and where you can drive yourself just makes life so much easier and I honestly think it was worth the trouble. Plus you are 18 - which I wasn't - so you already have the advantage of not having to waste time and money on driver's education like I did.
So if I were you, I would just go for it.

It might cost a little bit of money but you can remind your parents of how much easier getting a job will be for the both of you if you won't have to rely on them (or other people) for rides.
Just my thoughts.
Hope you figure things out.