My first two came from a pet store. (Pet"Smart"). One had bordetella, and I spent $400 treating it to keep him alive. Petsmart denied all wrongdoing. So no, I'd never go back there. Or any other pet store, now that I know more about small animal mills and the HUGE guinea pig overpopulation problem.
My 2nd pair came from the local rescue I volunteer with. They've both had a couple of health problems, and the rescue has been very good with helping me through it, offering to keep them after surgery, etc. I'd definitely adopt from our rescue again. The rescue has answered all of my questions, help me get booked in at the vet's, given me all kinds of help and support, even with the pigs that I didn't adopt from them.
My third pair came from a kill shelter in the western part of the state. I adopted them because they were spayed females. A third female that the person pulled from the shelter (also "spayed") had problems with ovarian cysts... which she shouldn't have had, because she was spayed. I'd probably not adopt from that shelter again.