The ACA Pacific Coast route shows 607 miles from SF to SD. Of course, that could vary a lot depending on where in SF and where in SD. Assuming you have the full 14 days available, that's about 43 miles a day.
San Fransisco to Santa Barbara is gong to be hilly. And this is at the beginning of your trip. These two factors will make it challenging. Santa Barbara to San Diego will not be as hilly and you'll be in a little better shape by then (if the first half of the trip didn't kill you).
For an avid cyclist, this would be a piece of cake. For a 65-year-old "casual biker", this would probably be a big stretch. But for a 22-year-old casual biker, my judgement is that this will be challenging but doable. Have fun and try to ride as much as you can between now and August 17. Start this afternoon! Assemble your gear, keep it as light as feasible, and take some of your rides with all your gear.
As far as planning, I'd buy the ACA Pacific Coast maps for section 4 and 5. Then just do what it says.
For further advice, please provide further details. What kind of bike do you have? What other outdoor activities do you do? Are you overweight? How tight is the budget? Are you planning to camp? Cook? Do you have camping experience? Are you known for your perseverance? (Actually, only the last question is important, and the answer must be "yes".)