Only a couple of the geckos in the Arroyo area are hostile initially, but if you are fighting near one of the neutral ones, they will join in. The best advice is to try to fight them one at a time, instead of all at once. Smoke can help a lot too, of course. Also, remember you can save in combat, so if you're really desperate you can reload after every miss to make sure you're always doing some damage.
For money, most of your cash in the early stages will be from dead raiders and such, and from drugs you can find lying around. Make a note of how much every item is worth, and determine whether an item's weight-to-value ratio makes it worth carrying around.