There are two ways to answer this question. The first is in an affirmative way. Radio wave dont suddenly get lazy and lie on the beach (well, maybe they do) in Hawaii, so any FRS (Family Radio Service) device will function just as well there as it does in Hawaii. So you could get one or more pairs of MR350R radios ($85/pair) and off you go.
The Talkabout MR350R Two-Way RadiosThe second way is this: You really might as well take a couple of long lengths of string and some tin cans. At their best, radios such as the Motorolas have a range of about two miles. And that is before you factor in hills, water, weak batteries, and a million other things that have an impact on radio reception. This isnt a knock on the radios, but you could literally be 100 yards from each other, over the crest of a ridge, and you might as well be trying to reach Cousin Kloogie on Alpha Centauri.
But, hey, maybe youre mostly surfing and hanging out on the beach, and the rest of your party is up on the main drag shopping for leather belts or something. They might work there. Then Motorolas I mention are nice. So are Rhino 530HCxs ($500/pair) which have on-board GPS units They also use GMRS (General Mobile Radio Service) frequencies, which have an ideal range of 14 miles. GMRS requires an FCC license, but cost is not prohibitive ($85 for five years) and the application process is not bad.
My own advice: Take your cell phones, have some party organization, and enjoy yourself. No one will get “lost.” Out of touch for an hour or two? Sure, why not? Determine a default regroup point and chill, bro.