Ok, so you probably won't see snow. Your footwear, be it boot or hiking sneaker, absolutely MUST be waterproof. You can get used on e-bay or invest in a good hiking sneaker like Merrell (what I have) or Salomon (what my boyfriend wears.)

Second, pack jeans if you want but you're going to be cold, wet, and annoyed if you don't have a shell. These are ok and affordable. Or here they are on Amazon, with more reviews.

You want base layers especially if you are going to snorkel. 2 bottoms 2 tops unless you are ok wearing the same for 4-5 days (I did, many base layers are designed to not stink. They keep you warm and dry very fast provided you avoid cotton. Wool or polyester. Polyester is cheaper and just as if not more warm than wool and importantly... doesn't stink.)

I have the woman's version of this, it is warm and awesome. I washed it during our trip and it dried in like 2 hours in our van.

If you want wool, I suggest Smartwool - but if you are from a warm climate and will never use it again, stick with a polyester version. They are honestly just as good.

Thermal bottoms. You can probably find other varieties of these on amazon, but do not buy anything from a no-name Chinese brand because you will be very disappointed. Like I said, you can totally do 5 days with ONE set of base layers because if you don't buy stuff with cotton in it, it dries very fast in case you must wash it.

Pack wool or wool blend socks. REI garage has a bunch of wool hiking socks. Like thermals if you wash the socks they will dry over night. So you don't need to bring 5 pairs but if you want to, go crazy. These are good in all climates for traveling and hiking not just cold weather.

So now you have your underwear on, socks, and base layers. Now you wear jeans or whatever you want. But if you are wearing denim or cotton pants... shell pants! Now you need a sweater or sweatshirt. Like this. Polyester. Dries fast. Looks cool. You can fit layers over or under.

And now... a jacket. With a hood. Here. This is also good in all weather. 85+ degrees humid and raining? Yeah, you can wear this and not sweat to death.

And that's about it. Layers layers layers layers! Outer layers must be waterproof. This is essential. If you want to put a cotton sweater over your base layers that is fine but make sure your jacket will keep you dry. Don't go insane buying new stuff, but if you can try to pick things you will use in the future. Have fun OP!!!