I was just there a few weeks ago.
First, I can't help you with anything about all-inclusive resorts (not my thing anywhere, and especially in an easy Mexican tourist town like this one, seems like a tremendous waste of money...there are oodles of great, inexpensive eating places nearby). To your other questions...
- exchange for peso ahead needed?
No, OMG no, and #@*!! no. Never, never do this (anywhere), you might as well just set fire to your money. Just use your own ATM "Debit" card from your bank/credit union at home, in an ATM upon arrival, to get money anytime you need it. The airport at "Los Cabos" in modern, clean, efficient, and I dare say "nice" - much nicer than almost any airport you will depart from in the USA. There are plenty of ATMs there, use one of them to pull cash (in Pesos, of course) from your home bank account after you land. Be sure to contact your bank (and credit card issuers) before you leave to give them a heads-up that you will be using your cards in mexico (so they don't suspect fraud and lock the card). Out and about, there are plenty of ATMs all over Cabo San Lucas and every town of any size that you might get to. Use one in a bank for better security. Never pay in dollars unless you want to greatly overpay.
- best way to get around outside resort? Or not?
Rent a car, or take a taxi, or walk or bike, depending on how far you're going, your location and tastes - same as anywhere else. Do not drink and drive, they take it very seriously.
- any short hiking trail?
- is it better to book ahead for tours or book onsight?
Can't help you with those (we didn't go hiking, other than walking on the beach, and we don't do organized tours, seeing no reason for that). Be aware that you are walking into the gaping maw of one of the world's most crass mass tourism destinations, so all of the worst that tourism can do will be offered to you repeatedly. Choose wisely. It's still a beautiful place, but IMHO you need to do your best to ignore and get past all the tourist trap places and experiences that will be marketed at you. Blow past all that stuff, make your own way -- it's an easy places to visit and explore, safe, friendly, informal, and it's a wonderful place.
Food? Too many to mention. A few we enjoyed: Mamas Royal Cafe is a great place for breakfasts. For incredible seafood (lunch/dinner) try Mariscos El Torito (deep in the downtown, away from the tourist zone, mostly for locals, and really awesome); for cheap, authentic, sloppy messy and completely delicious tacos right in the crass tourist zone hit Tacos Guss.
¡Vaya con dios!