I'd go to Baird Brothers on N. Valley Mills drive across from the HEB.
It's basically like a Genie Car wash, except it's self serve. If you don't vacuum you car, you don't even have to get out of it. It's not just a powerwash--they have the spinning brushes, etc. I think the washes range from $4 to about $12. Vacuums are free and run continuously.
However, if you're wanting a professinal detailing (which can run in the $100s of dollars), I'd just do that myself. Let Baird Brothers take care of 95% of everything with a wash, and then drive it home to spend a few hours in the garage taking care of the other 5% (the minute details: clay bar, polishing/waxing/making sure every last single spec of bird guts is cleaned off, etc).