I like the North Shore for shore diving best. However, these sites will not be diveable due to high surf while you are here.
Typically once mid September rolls around, I boat dive exclusively until mid May or so.
However, that's just my preference.
If you check out the shorediving.com website, you'll see several shore diving spots on the east side of the island that should be diveable while you're here. Many of those sites are not easy dives for various reasons. I choose not to dive them because I call it "billy goat diving" - the entrances/exits are rather strenuous for me. If you plan to check them out, the best is to have a good chat with someone very familiar with those sites to give you information on the easiest entrances/exits.
There was a thread several months back where we discussed some of these sites - do a search on bluemagoo's name and you'll find it. He detailed several of them.
The west side is usually diveable most of the year - Electric Beach is an easy shore dive, but has definite drawbacks as far as leaving your car. See MilitantMedic's recent post titled
"@)#@@%$(#@)""@#" - or something like that.
If you don't mind a pretty big surface swim, some people do Makaha Caverns as a shore dive. Personally, it's a bit too far for me to consider, but it's a thought. Makaha Caverns is my favorite dive site on the west side.