Only way to get onto the island is on Franklin St, near to the Convention Center, west of the St Pete Times Forum. Will definitely be blocked off during convention.
The island is mostly gated communities. You can go 2 blocks onto the island and then there are security check-points to get into the gated communities. The northern two blocks are a commercial district/chopping complex, to the northers-east end of the island, and hotels that span the length of the island, east to west. The accessible area ends at Knights Run Rd
The only way off the island is over a bridge on Beneficial Blvd, that runs into Channelside Dr right next to the commercial district of the Channel District, east of the St Pete times Forum.