From CalTrans:

The U.S. Marine Corps is planning to temporarily close the Camp Pendleton Bike Path—the only bike access between Las Pulgas Rd. and Basilone Rd. along Interstate 5 (I-5)— for military operations between this Monday, Mar. 28 and Friday, April 1, 2016. Under normal bike path closure circumstances Caltrans would open the freeway shoulders in this segment to bicyclists, however there is a construction project that has closed the shoulders of I-5 in that segment. Caltrans will provide a 24/7 on-call shuttle to carry bicyclists through the closures in the I-5 corridor between Oceanside and San Clemente. The phone number for the shuttle is (619)385-3267. Pick-up/drop-off locations are at Oceanside Harbor in the east parking lot (NW corner of the lot), at the park and ride lot at Las Pulgas Rd., and Basilone Rd.(at the south end of the Trestles bike path, where it meets Old Hwy 101). Signs at these locations will include the shuttle phone number. Please share this information and make your plans accordingly. We apologize for any inconveniences in advance.