We stayed last year for 5 days at Mission Bay RV Park. Like Campland (essentially next door to the west), it is very convenient to I-5 and Old Town, Balboa Park & Downtown or the beaches: Ocean Beach/Pt Loma via Ingram St & Mission and Pacific Garnet. They both have great access to the bay's bike system (front door of both parks) and the city in general. Marginal Wi-fi.
While MB RV Park was OK, it is simply a lot of asphalt on a corner of mission bay. Next time we'll stay at Campland (with some grass and landscaping as well as S Carlsbad SB or San Clements SB a bit further north in SD County. Last year we opted for Crystal Cove with it's fantastic view & sunsets over Catalina Is. However we prefer the two above as just didn't like all the traffic on Hwy 1 & Newport to the N.