Hi Lisa,
Your little one sounds just like mine! I have worked so hard to train him to go to sleep on his own in his crib, and now he naps so well, but ONLY in the crib. If I try to take a pack-n-play to my mom's house, or try to get him to sleep in his stroller, he will scream for hours. When we finally get home, he sees his crib, lets out a whimper, and falls right to sleep in it.
It definitely makes it difficult to get out. But I want to ditto the above post. Now that he can stay awake for 3 hours, it is much easier. So things will get better...
I am thinking of having him sleep in his pack-n-play in a different room in the house, just to get used to this. Has anyone else done this?