United has round-trip flights from Houston (IAH) to Guatemala (GUA) for $141-$161, NONSTOP. Flights in March, April, and May. A few weekend departures available.
Note: Carry-on bag is NOT allowed for free. Only a tiny personal item (like a laptop bag) is allowed for free. United’s personal item allowance of (9in x 10in x 17in) is smaller than most other airlines. You can avoid seat selection fees if you accept a randomly assigned seat at the gate. If you have the United MileagePlus credit card you should be able to avoid bag fees with the “free checked-bag” perk.