Bring beach/pool towels, goggles, pool toys and some dollars or pesos.  The Las Gaviotas complex often sells hamburgers, hotdogs, tacos, burritos, quesadillas, cervesas, and drinks at the pool side.

Las Gaviotas Physical Address
Careterra Libre Tiajuana-Ensenada Km.#41.5
Playas de Rosarito,BC Mexico 22710