Vistancia Driving Directions From I-5: East on Hwy 78; Exit San Marcos Blvd.; Left onto San Marcos Blvd; Left on Knoll Rd.; Right on Mission Rd.; Left on Marcos St. to the end. From I-15: West on Hwy 78; Exit San Marcos Blvd.; Straight across San Marcos Blvd. onto Knoll Rd.; Right on Mission Rd.; Left on Marcos St. to the end.