San Diego is probably the best city in America for making a quick trip to Mexico. Tijuana, which sits directly across the US - Mexico border, is can be reached by public transit. The San Diego Trolley's Blue Line provides service from downtown San Diego to the border. The trip on the trolley takes about 45 minutes from downtown. Once you reach the end of the line San Ysidro, follow the people and signs to the border crossing. It takes less than five minutes from the trolley stop to the border. Once across, it is either a 20 minute walk or a five minute cab ride to reach Av. Revolucion, the main tourist shopping street in Tijuana. If you take a car, avoid driving hassles and long waits when returning by parking in pay lots near the border and walking across. This also saves you the added expensive of purchasing Mexican insurance on the US side before you drive into Mexico. Be warned: you do not want to drive your car or a rental car into Mexico without this type of insurance. Otherwise, taxis, buses, and private car hires are all available. If traveling to Tijuana Airport, the Mexican airline Volaris operates a bus service between that airport and San Diego's Santa Fe Train Depot.
For a delightful, low-key alternative, drive 60 minutes on the American side to the small border crossing of Tecate home of the Tecate brewery. It's a short walk to the town square. Coming back, the line is usually shorter here at the pedestrian crossing. You can easily combine a trip to the train museum in nearby Campo with a quick trip across the border for lunch!
The greater San Diego County has a lot of smaller, more private beaches to the north e.g., Del Mar and Encinitas, and some great small towns to stay in and explore. Carlsbad, about 30 miles north on I-5, is home to the popular Legoland California theme park. Further east, the Imperial Valley and the California Desert give a change of scenery.
Julian is the largest and most popular mountain community in San Diego County. Also, nearby is Cuyamaca Rancho State Park and Palomar Mountain which has a large observatory. Beware, on hot summer days, the mountains are actually warmer than the city as they're next to the desert.
It's also relatively easy to get up to Los Angeles and other points in Southern California. Interstate 5 extends through the San Joaquin Valley of California, Oregon and Washington to the Canadian border. Although slower, California Route 1 Highway 1 or Pacific Coast Highway in most of Southern California and the US Route 101, through the Central Coast, Monterey Bay, and the San Francisco Bay Area, makes for more of a pleasant and fruitful trip. Be aware there's no gas/petrol or other services on I-5 between Oceanside and San Clemente for a distance of about 20 miles. Entry to Camp Pendleton generally requires a DOD decal or military ID.
There are no boats to Catalina Island Avalon within San Diego County. You'll have to go north into neighboring Orange County to the pier at Dana Point. By car, take I-5 to exit #79 Pacific Coast Hwy 1 make reservations.
Temecula Wine Country is located about 60 minutes northeast of San Diego and makes a good day trip. There are about thirty wineries with tasting rooms located fairly close to each other. One hour further is the mountain resort of Idyllwild which features shopping and outdoor activities in an alpine forest.
