~ ~ ~ Warning! Potential Spoiler! ~ ~ ~
Well anyway, for what it's worth, here goes. After starting and saving your game, try to get $1000 in your pocket so that you can purchase Skumole Shack on the west side. Drive an ambulance, because it works the best, to Starfish Island and park it with the passenger side against the gate. Back up on to the sidewalk keeping the vehicle against the gate and the yard fence; cram it in tight. You should be on the north side of the road facing south. Get out and jump on to the hood, then the roof. It looks like you could easily jump over the fence into the yard but you can not; the collision geometry is much higher than it looks, like the road barricades. Instead, get as much of a running start as you can and jump through the narrow gap between the arch and the yard fence. A perfect jump and you can land right on the other side. A mediocre jump will get you kind of wedged in between. Run, jump, wiggle, squirm until you pop through to the other side. A lousy jump will land you between the gate and the ambulance and you will have to run, push, shove, cuss, and swear to weasel back to the street to try again.
So much for the easy part. Now get to the other side of Starfish Island. You need to get into the yard of the house along the west shore that is north of the east-west road; the one with the locked front gate. Go to the house north of it, the one with the tennis court, and use the garbage dumpster to jump over the wall and hedge. Walk as far west as you can but stay to the north. Try to get the "Welcome" screen to come and go so that it doesn't throw you off later. Now look to the south towards the bridge. It should not be long and you will see boats heading your way. Big ones will get stuck under the bridge. If that happens, look/move around until a different spawns. As soon as a small enough boat passes under the bridge it will abruptly crash into the island, like the game doesn't know that it is there. Now is your chance! Time it right and FALL on to the boat. Try not to jump because you will probably end up going too far and becoming shark chow! The easiest boat to try this with is a "Rio" because they are flat and slow. A speedboat can work, but they sometimes flip upside down quickly and easily right around the time that you would try to land on it. A dinghy is practically suicidal. If you land safely on the boat, the owner will always get scared and jump into the water. Hit the "ENTER" control to get safely to the steering wheel.
You can now go to any part of Vice City that you wish. You will not become "instant wanted" like in San Andreas (that was just kind of f-tarded). There is a convenient pier just across the channel, but jumping from a boat to a pier is kind of risky. The nearest places to just ground your boat and hop out are the Boatyard to the south and all the way to the north side of Downtown by dirt track.
Purchase Skumole Shack and save your game. Of course there is the handy-dandy police helicopter nearby for your own personal use, say for getting previously inaccessible high altitude hidden packages.
ALL hidden packages can now be obtained.
ALL rampages can be completed.
There are 2 Unique Jumps that can not be done because the can not be accessed until a certain mission is started.
The 3 stadium events can now be done.
You now have easy access to a firetruck, but the Firefighter mission can not be done on the west side because the targets will be on the east side; the same for the Ambulance Mission.
I don't remember if the Pizza Delivery Mission can be done either, I do not think so.
The Taxi Mission and Dirt Track Races can be done.
Even though it would be tempting, I would NOT purchase Hyman Condo until you have at least 70 hidden packages found. If I remember correctly, the power ups will not appear at the condo if you purchase it first. Need verification of this.
If you get busted or wasted you will end up back on the east side.
Try to get at least 80 hidden package found. That way if you end up stuck back on the east side for some reason you will have a Sea Sparrow to use from Diaz' mansion instead of trying to pirate a boat by falling on it.
And that's that. It is not as tough or involved as it may seem once you have done it a few times.