March or April and other Phuket questions.

I'm about ready to pick my first Star Clipper cruise which will also be my first visit to Thailand. It will be solo so I'm only considering dates in the no solo supplement special. The March or April dates would work for me.

Is March or April better? The April round trips start or end during Songkran (Thai new year) so if I picked April, it would be the April 6 date so that the festival doesn't interfere with enjoying a pre-cruise land stay. The cruise ends on April 13 which is the first day of Songkran. Will that be an issue?

Earlier in the year, my husband and I are going on a Panama Canal and Costa Rica cruise. The CDC site says Thailand requires a yellow fever vaccination if traveling from countries on the list with a risk of yellow fever transmission. Panama is on the list but with a note that the risk only applies to part of the country and the canal area is supposed to be okay so I don't think I need the vaccine for health reasons. (I'll be double checking that with my doctor closer to the trip.) Do I need the vaccine to go to Thailand? Does the requirement only apply when traveling directly from a country on the list or would a visit 2 to 3 months before also require it?

Any suggestions on good places to stay in Phuket?