by Eli » 25 Jan 2011, 02:38
Regarding visas, you will not need anything if your stay is shorter than 90 days if you are a U.S. citizen.
EDIT
Then it does not matter where you travel from. What matters is your nationality. You will need to obtain a visa from the Bulgarian consulate in the U.S. or Mexico even for the entry. If you want to work there, you will need a work permit too but if you just want to stay there, you will need a visitor visa.