Yes, most likely you'll share (unless your contract specifies a single)
Yes, you can bring a keyboard to practice. If a veune is quiet or closed during a port day, you usually can practice there also. On my ships, the muso's practice in the orchestra pit or backstage on the theater's keyboards or grands.
Yes on internet. All ships have some sort of crew internet cafe (per minute charge). I'd advise taking your own laptop and finding cafes or hot spots in the ports (there's many free wifi spots everywhere, and for some reason, the muso's are the first ones to find them)
check out these links
(esp rules and attitude )
and for the other side of coin but a good description of muso's life on board (and a bit anti the website above)
go to google groups
and type in "bass player cruise"
- there's a thread called "cruise ship experiences" in alt.guitar.bass about muso's life onboard. Coming from being on ships for 5 years, I can attest this is VERY accurate as far as the good and bad sides of cruise life. The guys responding are a bit . . um . . bitter, but if you can deal with what you read, you'll be OK . .