Human actions are changing both terrestrial and aquatic ecosystems, and ultimately causing increased rates of species extinctions. Furthermore, a majority of species' population sizes and/or geographic ranges are declining worldwide due to anthropogenic stressors. Many of the stressors that impact rocky intertidal ecosystems result from increasing urbanization, recreational activities, and harvest of species at the shore. San Diego's temperate coastal climate, in particular, attracts large numbers of visitors who conduct recreational activities and harvest species in the rocky intertidal zone. As a result, following years of planning, several marine areas around San Diego have been protected from harvest as part of a network of Marine Protected Areas (MPAs), though it is unclear how this impacts the way the public uses the ecosystem. This study investigates (1) visitor knowledge about MPAs in San Diego County, (2) visitor activities inside and outside these MPAs and (3) species composition in three MPA intertidal locations and three nearby non-MPA intertidal locations. Visitor intensity ranged between eight and 70 visitors per 10-minute periods during low tides, with tide pooling being the most common activity; 83% of beachgoers engaged in this activity. The diversity of intertidal organisms did not differ between MPA and non-MPA sites, and beachgoers were observed collecting in both habitats, with collection intensity ranging between 0.01 and 0.98 collectors per 10-minute period. Although collection of any intertidal organisms is prohibited in MPAs, visitors were nevertheless seen taking crabs, abalone, and other snails from these areas. Additionally, in-person surveys of beachgoers suggest that the main problems facing rocky intertidal MPAs in San Diego County are (1) lack of effective enforcement, (2) inadequate signage, and (3) lack of visitor knowledge about MPA no-take regulations. This thesis confirms that enforcement of regulations at San Diego rocky intertidal sites is virtually absent and that enforcement would be most effective on weekends and at sites that are most highly visited. Therefore, improvements to management strategies are recommended, such as additional efforts to educate visitors before and during visitation, expanded docent programs, and increased enforcement of regulations.