While there may well be many good agents in SP, the system is not quite the same as you may be used to: There is no MLS in Belize, so it is not uncommon to see the same property offered by several agents, not always at the same price.
Take a trip down, look at several areas, and “interview” agents: What type of amenities are you looking for, and will you supplement cost of ownership by renting, even occasionally? Very few properties in San Pedro will offer positive cash flow, so your financial ability to buy and hold a second home may define the type of property you ultimately buy.
It took me 5 trips over an 18 month period, and a couple of false starts before finding the property that we have ended up buying: with each trip the criteria changed slightly, as did the perception of how much time we would spend each year in San Pedro
A buyer’s agency agreement with someone you feel comfortable with would at least shift the fiduciary responsibility to working in your best interests as opposed to the sellers.