you're going to be sort of inconveniently located, in the bronx, if you plan to hang out in manhattan most of the time. Well, maybe not inconvenient, but sort of far away. Subways do go to the bronx, but it's going to be a long ride into manhattan. not sure where in the bronx you will be so I can't be very specific.
[
nyc.taxiwiz.com]
try that page to get your cab fare from laguardia to your place in the bronx