IT was not easy but we started by warning him all excited at no so unfamiliar places like grandma's or some uncles. I got to the point to even visiting the uncle one day before the party was being held (yep, i got the funny looks and the rolling eyes but i've developed an I DONT CARE back LOL) so he'd got familiarized with the room he'd be sleeping in. I still visit with the whole parafernalia: pack n play, sheets, pillows, ocean wonders, 3 stuffed animals, pj's, ipod, ipod amplifyier (so he can have HIS music), darkening curtains (cause some homes we visit don'thave them LOL). I try to arrive at least 30 mins before nap time (i don't care if the hosts are still preparing the gathering... no wonders i dont get invited so often LOL... i just do this with really close family) so he gets used to the environment. I make a big fuss of it (and keep warning him throughout the day): HOW exciting WE ALL ARE GOING TO NAP AT AUNT's X!!!!!! woooow... will we take Monkey? oh yes, let's take him... The first 2-3 times he'd have trouble settling but i'd stay next to the crib, reassuring and holding his hand, pretending i was asleep too. He usually naps for 2 hours but the first times he'd nap for 1-1.5 hours. It was just a matter of practice and after the first 3 times he got the hint and now he'll sleep anywhere (as long as it's a bedroom and it's not too loud, i mask the outside sound with the music). HTH and give it a try! you will not regret it!
PS edited to add if he has never slept in the pack and play try a few naps at home, with the same routine in his room, sort of a piyama party, make some stuffed animal to sleep in his crib so he can sleep in the pack and play.
