Ask any of the Marine instructors - they will be able to fill you in since squadrons generally deploy as a "composite" squadron (46's, 53's, Cobras, Hueys, and Harriers all under the same squadron CO). Still a few years away for the 4 bladed Cobra "Z" and 4 bladed Huey "Y" - skid27 can probably answer that better. On the East and West Coast's, you will attach to a 46 squadron - generally 4 Cobras and 2 Hueys (if the threat dictates, possibly more Cobras - we had 8 in Somalia). You will then pump overseas on a standard 6 month deployment. I'm not quite as up to date on the UDP's (unit deployment programs) to Okinawa but generally you go there for 6 months to a year and attach to the 31st MEU.
Almost always, you will not be able to leave a fleet squadron until you have done 2 pumps - although some will be "chosen" for a FAC tour. With the massive amount of deployments over the last 2 years, the OCD is probably a mess right now. You also do not want to float right away because it takes a year or so in your squadron to get up to speed on your fleet platform - lieutenants are still in the learning mode until you get your quals.
Finally, Cobras do the vast majority of the shooting and attack missions. Hueys do a lot of VIP missions and command & control.