I was taught that on the street, both brakes or none. Steady pressure on the front vs. a "grab" to avoild lockup. Practice is your friend, as every bike's brakes feel different.
Have you taken a safety course? If not and if they offer them in Guatemala, take one. Otherwise, find an empty lot and purposefully practice locking up the back brake, so you learn and know how it feels. Then practice locking it up and then backing off. Also practice the squeeze of the front brake, and learn how much you can get away with (don't, no matter what, lock up that front brake!)