Los Angeles and San Francisco are about 347 miles apart by road. Split the difference and you arrive near San Jose, the city closest to the halfway point between them. That puts roughly 6 hr 24 min of driving on the Los Angeles side and 1 hr 3 min on the San Francisco side — the fairest single meeting point among the cities near the middle.
That's a half-day drive from each side, so San Jose suits an overnight or a weekend rather than a quick coffee — long enough to want a reason to stay, short enough to drive.
If San Jose doesn't have what you're after, Sacramento and San Diego are also close to the midpoint and worth a look — each keeps the drive reasonably balanced between Los Angeles and San Francisco.
City descriptions adapted from Wikipedia (CC BY-SA); photos via Wikimedia Commons, credited above.