Why not call Costa and ask them. I know other cruise companies provide the visa on board but each is different. Have you checked cruise critic to see if there are fellow cruisers you can meet up with for shore excursions etc? Go to the Roll Call section. And the Ports of Call section is very very useful for the various ports and ideas of what to do.
Could you give your reviews on costa allergo as my husband and i are going on it in may 08 but the ship has not had a very good review.my name is Mrs Laird.
We have just returned our cruise on Allegra. Do not worry about the visa - all taken care of onboard and they will advise you. They do keep your passports and they are stamped but you have a copy to take ashore with you. The visa for chine (Sanya) can be obtained on board at a cost of £35 each, however if you go on a tour cost is included or best option is to book the shuttle bus into town at 20 euros which includes the visa. Make sure you do book in time as some people where unable to go ashore as they missed the deadline. Once in the town centre you can get a taxi and have a trip around the area. Not the best of ports but you may still want to go ashore. Hope this helps if you require further info please contact firstname.lastname@example.org.