Shilo,
The problem with snorkeling in Monterey is that visibility is hit and miss. 10-15 ft of visibility is considered good. You can snorkel - but I don't think you will be seeing much. Unfortunately - to really see something, you need to dive. Also - the water at Monterey is pretty cold (47-55F), so you will need at least a 7mm wetsuit to keep warm.
Breakwater (AKA Coast Guard Pier) is relatively calm water - but the visibility can be very poor due to all the scuba students kicking up silts. Pt. Lobos is another good spot, but you will have to book WAY in advance for diving (Limit 15 diver pairs per day). I don't know about snorkeling. But if you want to go on a scenic walk - Pt Lobos is great, and they don't have limits for that.
If you really want to snorkel, go to some tropical water.
Minh