Returned from trip to 7-day trip to rural honduras. Now some small, round, itchy bumps appearing scattered on arms, top of legs, calves. What is this?

Bug bites. What you are describing could be bug bites of some type due to the nonspecific location. Because of the tropical climate, it could be any number of arthropods. You may want to see a physician for treatment since the number is so high extending over a fairly large body surface area. Additionally, watch for any signs of infection--fevers, night sweats or redness and enlargement of the actual bumps.