I never see any hot air balloons on the east side of the Sandia Mountains. The prevailing winds in Albuquerque, where the balloons launch, blow from west to east. When the west wind reaches the mountain top, it spills over and forms a rotor wind like a wave crashing on a beach.
Some pilots do cross the mountains but only when the conditions are just right.
Liz Appelman flies with the Rainbow Ryders and says it takes planning. Balloonists need winds strong enough and in the right direction to get over the mountain with a thousand-foot safe margin, to a road for the chase crew, and to a nice landing spot free of trees. It has been done fairly often Liz says.