Take 290 West towards Fredericksburg. Follow signs for Fredericksburg once you arrived in Johnson City. About 1 mile before Fredericksburg, turn left on Old San Antonio Rd. Bikinis, TX is about 7 miles down on your left.
From San Antonio:
Take I-10 West towards Comfort, Take exit 523 to 87 North. Follow 87 until you get to Fredericksburg, then take a right on 290. After about 2 miles, take a right onto Old San Antonio Rd. Bikinis, TX is about 7 miles down on your left.