We got back 1/24, moved up our trip so that we didn't have to test before return. I think that many resorts are going to be offering on site testing, but you still have to weigh the risk of testing positive (or a false positive) and being stuck in Mexico.
No issues at the resort, I don't think that I every saw an employee without a properly worn commercial mask. Some limitations on bars/restaurants at the resort (all inclusive) because of low occupancy. Buffet lines were served by staff instead of scoop your own. Our resort was maybe 20% capacity. Beach and pool has plenty of space to distance. Overall, felt very safe, but I'm not sure that I would go now with the testing requirement in place.