Both Nassau and Suffolk County are usually divided into the North Shore, which is on the Long Island Sound, and South Shore, which is on the Atlantic Ocean.
Jones Beach 
Nassau County is the second largest county by square mile on Long Island (Suffolk being the largest by far). It is sandwiched between Suffolk County and Queens County. The County Seat is in Mineola. Nassau County also has several beaches, including Jones Beach and Long Beach. You can also visit the downtown areas of each village. There are typically many shops and sometimes even restaurants in those areas.
English is widely understood. Hempstead, Uniondale, New Cassel, Westbury and Freeport have large Spanish-speaking populations.
Take the Long Island Railroad or drive in via the Long Island Expressway, Northern State Parkway, Southern State Parkway, or Sunrise Highway.
Getting around is very easy by car, especially with the presence of the Long Island Expressway (commonly referred to as the LIE in the area) and several other parkways.
All American Hamburger Drive-In in Massapequa is a vintage, 1950's-style burger joint.
Nassau County is in general a safe place to visit. As anywhere, just use basic common sense; this is the average suburban county. Crimes, if any, usually occur in Hempstead, Freeport, Roosevelt, Uniondale, and the Queens border of Valley Stream and Elmont.