You can definitely get by with a 5mm but 7 is best for a dedicated, year round Washington suit. If you run hot you can even get by with less, but just know you won't last very long.
Washington regs are restricted and tough to understand. Get a copy in paper form and look at the bottom fish section for any where you might want to dive.
Crab is closed now for Puget Sound and the Straight, but might open again on October 1. Check here for updates:
http://wdfw.wa.gov/fishing/shellfish/crab/
Pretty much every where is open to spear for perch, greenling and flounder. Little fish but they taste fine and are something to pursue while underwater if you really want to get wet and check out a new environment.
Some people ignore these reports, but look here for shellfish biotoxin updates:
https://fortress.wa.gov/doh/eh/maps/.../biotoxin.html
Have fun, PNW diving is really great if conditions allow even if you can't spear lots of big fish.