For workout places, just find a park with a playground and do pull-ups, push-ups, squats, sit-ups, burpees, etc, lots of options. You could also drop by a Crossfit box if you CF.

Food is pretty easy in NYC, there a lot of restaurants and you can just sub out the pasta/starches for vegetables. An overlooked type of restaurant is BBQ. I love BBQ and its a perfectly paleo food, just make sure to not use sauce. If the meat is true BBQ it shouldn't need it, the sauce actually makes it worse-tasting.

Melissa McEwen's blog http://huntgatherlove.com/ has some New-York-City-specific tips, mostly on market locations. Check her out.

Re BBQ: Fette Sau in Williamsburg...another spot thats super paleo: Prime Meats in Carroll Gardens

Where does she live in Brooklyn? Grand Army Plaza near Park Slope has a farmers market every Saturday. There is a farmers market in Brooklyn Heights, but I don't know what days. There is always the farmers market in Union Square (in Manhattan). Is your sister a member of the Park Slope Food Co-op? Perlandra in Brooklyn Heights has organic and natural foods, but be prepared to pay a ton of money. Union Market also has good stuff-also very expensive. There are several chains. Trader Joes is on Atlantic and Court Street. They have some organic meats and tons of non-organic meats. Fairway in Red Hook is supposed to carry organic meats but I didn't see any on my last trip there. They are also an enormous grocery store, but avoid going on weekends. Places to eat that are decent: Romans in Fort Greene. Prime Meats (mentioned in another post) in Carroll Gardens and its brother Frankies has a steak drizzled with olive oil. The rest sadly, is mainly pasta. Flatbush Farm has sustainable meat and a garden outside. Have a great time and good luck!