I never get prints done myself, but a friend of mine gets a lot of prints done and he also gets them done at wal-mart. He has had many 8x10s done there and they look great. He does do a lot of work before printing though, and I don't know what resolution, size, etc.
Maybe ask someone at the counter. My buddy says that they are pretty helpful there...at least at the store he goes to.
BTW...I love your avatar shot