Just because you have him neutered doesn't mean that they will be compatible. It depends more on the personalities of the individual cavies. Having said that, a neutered male/intact female can be a lovely pair. Chester had been a solo piggy for a year since his brother died. The local pet stores know how much I love cavies and an owner once gave me a little female because she was a surrender and he wanted her to have a good home.
I brought her home and introduced her to my very mellow Chester. He was absolutely indifferent to her! He wasn't hostile, but just totally had no interest in interacting with her at all. I returned her to the pet store that same day. Fast forward about two months and I set out to find him a female cagemate. I came home with a 3 mo. old Texel and it was literally love-at-first-sight for both of them.
Neutering is quite safe in the hands of an experienced cavy-savvy vet. If you choose to have your male neutered, you will need to wait about four weeks until all of the resident sperm have died before putting them together. If you do the proper introductions, you have a good chance of them being able to live happily in the same cage.
