Dave-
I spent 5 years living in that general area as a grad student through 2009 and have spent considerable time in all of the areas mentioned and then some. Here are my thoughts:
1. Diablo really is pretty cool - a singular peak/ridge in the middle of a vast expanse of flatness. A bit like Katahdin, in a way. It will be HOT and DRY. It doesn't rain in north/central CA from May until December most years, so it is always brown all summer. This is just part of the desert landscape and you can find tremendous beauty in the browns and golds in the same way you can find beauty in barren tundra above treeline in the Whites. There are a couple of pretty long loop hikes possible that pass over all of the sub-peaks on the ridge. A full day with boots on the ground, if that's what you want.
2. Point Reyes is well worth your time. My favorite hike is the hike to Alemere falls and Wildcat Beach via Bass Lake. See
this synopsis. You start in a eucalyptus grove, a smell you will never forget. Then a lot of dry, sandy brown and gold hiking to Bass Lake, which you can swim in (you'll return the same way, so we usually took a dip on the way back - note that you may encounter people sans bathing suits. This is true of any place outside of a quarter mile radius of a parking lot in this part of CA.). Eventually you get out to some smaller ponds and to the coast. To avoid poison oak, you can hike to Wildcat Beach and then hike the beach to the falls, rather than taking the short cut directly to the falls - a path that is consistently choked with poison oak. Return the way you came.
3. Muir woods is unique and pretty. But there is a paved path through it that you follow. Consequently, to me, it feels like the summit of Mt. Washington. Doesn't mean you shouldn't go, just know what to expect.
4. Which brings me to the weather. Expect foggy and windy and cold anytime you're within a mile of the coast. Sometimes it clears. Probably as often as it does on the summit of Washington. As a matter of fact, you'd do well to pack the same kind of clothing for a stroll through SF and across the Golden Gate Bridge as you would for a hike to the summit of Washington in the summer. Also, you may never get a view beyond a quarter of a mile. At all other times, expect it to be blazing hot. There is no in between.
5. If you're right in SF, go to Baker Beach. The view of the Golden Gate bridge cannot be beat. Note what I said in point 2 above regarding bathing suits. Also close by are Battery Spencer and Hawk Hill: right after you cross the Golden Gate bridge into Marin, take the first exit and head up the big hill to the Marin Headlands. The view down to the bridge and across the bay to SF is truly special.
6. The ocean is very cold. It doesn't change much from winter to summer, and usually stays around 55 degrees F.
Enjoy,
Brian
I've done Alcatraz years ago and we're both past our clubbing days.
