Cancun is an extremely large area geographically. You should probably stay within the hotel zone. The hotel is kind of shaped like the number seven. Most of the shopping restaurants and bars are at the top of the 7.
Most travelers stay at AI’s. Most travelers do not stay in downtown Cancun. The RIU is close to shopping and entertainment. So you may want to begin there and work your way down (south) the 7 shaped hotel zone.
I try to avoid AI’s... just not my thing.
I actually have friends who live in downtown Cancun that we will be spending time with, that’s why we are going there:)
I’m curious about Puerto Juarez? Is it mainly residential? Are there much for restaurants and shops in the area?
Public buses are the mode of transportation in the hotel zone. Very inexpensive. No need to walk. There's a small hotel in km 5.5 that's not too expensive and also walking distance to Playa Langosta. I believe it's named something Real. It's on the lagoon side of the road. Also across the street there's Casa Maya great beach and make sure it has at least a microwave and coffemaker.