Cancun is the easiest to fly into. From Cancun airport you have around a 4 hour drive. You can also fly into Chetumal which is a closer drive, but good flights are hard to come by.
Rent a car online if you want to have the freedom to explore. If you want to save some cash, you can share a shuttle or take the bus (below). Either way, we suggest getting in touch with other guests and carpooling. The drive is super straight forward on a major highway. We have done it many times, its easy to navigate (literally straight on one road 90% of the time), well maintained and safe. (Watch for the random speed bumps though)
In order of cost; 1. The ADO bus to Bacalar is around $35 USD and takes a little longer (5-7 hours) but they are nice, comfy and you can sleep. Check ADO.com.mx 2. You can plan ahead to arrive with other guests and get a shuttle with others to share and go directly there and save some cash and time. 3. You can grab a private taxi at the airport and pay $200-250 one way (you could rent a car for this much).
Being that Bacalar is a smaller and less known, less touristy location (for now), you can stay in a luxury hotel or AirBnB for $150-200 a night. You can also save money and stay in a nice Eco-Hotel on the lagoon for around $65-100 a night. Or you can save all the cash and roll up in a hostel for $15-45 a night. We don't have specific recommendations of hotels, but suggest staying within the town area for convenience, especially if you don't have a car. Bacalar is known for it's welcoming-ness and safety, so there aren't really bad options for hotels, but always check those reviews. If you need further help, we have a concierge that can answer any questions, just message us.