Cavy House Guinea Pig Rescue

This is in SF. You can adopt a fixed guinea pig from them. Already fixed. Can adopt a couple since they are social.

Plus, even if you are not in SF, the link has lots of good info.

Hamsters: nocturnal, dry poop, need smaller space, solitary.
Guinea pigs: diurnal, wet poop, need a lot of space, very very social.

I have only had hamsters but I have looked into guinea pigs and they are totally adorable!