Hi, Colleen! You can absolutely visit any of the Walt Disney World resort hotels, even if you are not a guest of the hotels! The resorts have shops, restaurants, and some have amazing art work and architecture - not to mention beautiful scenery - that would be great to go and see!
Animal Kingdom Lodge has a beautiful vantage point from where you can see the animals on the savannah and listen to the African story tellers. The resort itself is home to some beautiful pieces of African artwork. The Polynesian has absolutely lush tropical grounds that are a pleasure for the senses to walk around. Don't miss the incredible fireplace and the totem poles at Wilderness Lodge!
To gain access to the resorts, you just need to go through the security gate. Let the security guard know that you'd like to take some time to browse the shops and see the resort, and they will give you a pass that allows you park for up to three hours in the resort parking lot. If you are at one of the monorail resorts, this may be enough time to browse all three and only have to park once! Take the monorail in between.
If you can squeeze in an evening visit to the Boardwalk resort area, you'll likely find a variety of performers entertaining Boardwalk guests. You may even get a glimpse of some of Illuminations from EPCOT.
Have a wonderful time on your vacation!