So, one way to do it is pull up Google maps and just check your tentative dates on each hotel down the Harbor "strip" across from the east entrance. Go to the individual websites of the hotel (not, like, Expedia or whatever) and see what they have available. Start with HoJo at the top, do Courtyard, Fairfield Inn, Camelot, Tropicana, BWPPI, Park Vue, Desert Inn, Del Sol, etc. down to the corner at Katella, and throw in Candy Cane Inn (because it's a huge favorite even though a bit farther) and just see what they have. Because I'm here to tell you, there's nothing like being within a 10 minute walk. It's so sweet to be able to ditch the hot, crowded park in the middle of the day, walk back and take a break, then come back refreshed without fussing with shuttle, buses, ubers, etc. That's my method for research. I've stayed at Hojo (nice waterpark) and at Desert Inn twice (very plain, but clean, and right at the crosswalk, usually the cheapest).