Yes.  Guinea pigs (unlike hamsters and some other pets) are
     sociable creatures, and are usually all the happier for company,
     although they may ignore their humans more as a result.  If you
     don't have a lot of time to spend with your guinea pig, or are
     gone for much of the day, your guinea pig may be a lot happier if
     you get him or her a friend.  Same-sex groups, of either sex,
     usually get along fine if given sufficient room, although from
     anecdotal evidence females seem to be slightly more reliable in
     this respect than males.  A male and a female are naturally the
     best company for each other, but unless you want your female to
     be constantly making little guinea pigs, you will have to neuter
     one or both of them.