At the risk of saying something both obvious and useless . . . it depends on the WOD?
Some workouts require little more than a pullup bar and a place to do burpees . . . others *should* have 12' x 17' for one person (e.g., Linda).
I think you'd be able to do some WODs with 3 people in 12x17, but certainly not all. Fresno's not too bad in winter, but gets plenty hot in summer (I was born there
) . . . can you drag stuff outside?