I'm currently level 5, I basically skip all of the side quests in order to find the GECK. Still have yet to find vault 15, but found San Francisco. Sorry about my first post, I never use cheats (besides the contra code), and I never get angry over video games. I just exaggerated the whole post. I've played the first game when it was launched 12 years ago. This is my first time playing number 2. Does the car get rid of random events? Where can I find it?
Backtrack. Get some money (by looting items from killed enemies from random encounters for instance, which is also a good way of earning some experience you really could use at this point), do some sidequests, most of them don't take that long and keep you inside of the town. You can get the car in the Den, but to actually use it you need a part that's over in Gecko. To get that part, you'll have to talk to the woman in maintenance in Vault City and get her the items she needs. Really, just doing some small sidequests really helps a lot. After you find enough money and items, go gear up, San Francisco would probably be best. Give yourself and possibly your companions some decent armor and weapons, and you might even be able to kill the troops on your way.
If it's still not working, countrybluegrass's idea is a good one, though it does get tedious.