Middlesex County is squarely in the center of New Jersey, about midway between New York City and Philadelphia. Population is approximately 750,000. Area is about 318 sq. miles covering 25 cities and towns.
You can find a map of the county (PDF) at this state government site.
Middlesex County is served by major interstate highways, including US 1, I-295, I-287, the New Jersey Turnpike (I-95) and Garden State Parkway.
New Jersey Transit buses travel throughout the county.
NJ Transit buses run throughout the county. Driving by private car is easy and parking is generally plentiful. Rush hour congestion across major arteries (such as the Raritan River Bridge between New Brunswick and Highland Park) can be exasperating if you are in a hurry.