Do you want to go up, then down, or down then up? The lower parking lot is accessible from Hwy 1, the upper from 35/skyline. Are you coming direct from San Diego to the hike, or starting from accommodation in HMB? Assuming you are coming North from SD, 5 to 135 (or is it 153?) pacheco pass, then 101 to 84, which will connect you to 35 or 1. 84 normally runs faster than 92 on weekend mornings in the summer. If you're starting from HMB, and want the lower parking lot, i find it easier heading south on 1 to Verde, and approach that way. If you take the road from behind the fire station, Higgins Canyon, is long and wiggly. The lower lot only has about 6 spaces, but people park along the first half mile of road before.
Parking at Purisima is from sunup to sundown at the trail. Seems people can park on the street outside the park. It is pretty remote. Have fun it's a beautiful hike
Purisima is off of highway 92 which is accessible from via 101, 280, and highway one. It wouldn't really matter which one you pick. There's ample parking - there's a good sized lot and plenty of roadside parking immediately adjacent when the lot gets full.
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