hawaii without car

Hi!!!
I'll be in Hawaii in spring break( Oahu,Kauai and Maui) and i need some help:

1) I do not have a driver license. anybody knows a cheap tour operator to do some tours around the islands(hiking,scubba diving,surf....)

2)What are the best part of the island to find a place to sleep without a car( beautiful beach close by....)

3) Anybody knows a nice hostel to stay were hopefully i will be able to meet other travellers?( i am going alone)

Thanks in advance

Hi

I've been to Oahu and the public buses cover much of the island and are easy to find and use. Worked for me for the two days I was there.

-Nigel-