USA Transfers shuttle company run all up and down the zone going far south. If you're looking for something cheap, there's no such thing with transfer/shuttle companies unless you double up with someone else. I used them before and they worked out just fine. I had planned on using them for a resort to resort transfer but ended up just staying at the original resort.

https://www.entertainment-plus.net/affiliate_1082

*Also Uber and the Taxi union got into a major dispute a few years ago, so that's why it's not an option in many areas other than downtown (original town of Cancun). You can get Ubers from downtown Cancun to the hotel zone and to the airport etc, but not the opposite.