Mexico is a bit tricky because of the wording they use.
That website says two things:
#1. Permanent residents of United States of America must present their Permanent Resident Card and one of the following documents: valid Passport or Refugee Travel Document.
#2. Effective May 2016 all those foreign nationals, regardless of their nationality, visiting Mexico for tourism, business or transit are NOT required to obtain a Mexican visa IF they hold a valid (non-expired) Visa or Permanent Residence of any of this countries: United States of America, [..].
So it says you need a GC, but it also says you don't if you have an unexpired visa or permanent residence, which being a refugee counts as "permanent residence" and your RTD is proof of that, refugee status doesn't expire. I have also heard reports of people traveling to Mexico only using RTD, but not sure if by plane, car, cruise, etc. Sometimes the rules vary depending on how you're traveling. So I would say check with Mexican consulate or Timactic.
For Dominican Republic, assuming that's what you meant, IF I remember correctly you can travel there only with RTD as long as you have a return ticket. Again check embassy or consulate or Timactic before purchasing anything.