There are
2,706 mi
from San Marcos, CA to Bethlehem, PA
That's the driving distance. It would take 2 days to go from San Marcos, California to Bethlehem, Pennsylvania.
The flight distance (direct flight from San Marcos, CA to Bethlehem, PA) is 2,343.99 mi.
2,706 mi = 4,354.71 kms