What kinds of things do you like? Friday Harbor is the "big town" feel in the area. Roche Harbor has the rich flavor. The country general store in Blind Bay has the small island feel. Jones Island, Doe Island, James Island are just some of the state parks accessible only by boat. Garrison Bay just south of Roche Harbor has the Pig War
history.
I'd suggest get a cruising guide to see what interests you the most.
On the way south on the west side of Whidbey there's Port Townsend, Mats Mats, Port Ludlow, and Kingston. Lots of people like Mats Mats, but the entrance can be tricky. Port Ludlow has a resort at the marina, but I like to
anchor south of the two islands at the west end of the bay. Used to be all trees, now you're looking at the backyards of houses but I still like it. Kingston and Port Townsend are normal small towns.
Everything Le Tour said about night sailing is true. I quite often begin a trip Friday night to avoid the traffic in the locks, have at times left in the middle of the night to catch tides, and have had a couple of bumps in the night. I'd say night sailing depends on your experience level. I go out quite a bit with people in my club that are taking
classes, so I try to let them get some experience. Last trip I asked one person if she had checked for traffic, she said she had been too busy, but promptly looked around. Reported all clear when to me the lights of two tugs with tows and a ship were visible, and one of the tugs was a potential ROW issue.
One friend of mine avoids night
sails on spring tides on the theory that more
logs are washed off the beach during those times.
Catch the tides right as the flood is north in the San Juans and south in the main part of the sound, so catch it right on the change and never slow down.
GPS never said less than 8 knots from San Juans to south of Admiralty Inlet last time I came back.
John