As is true for much of the United States, crime is a problem in the inner cities, while city outskirts, suburbs, and the countryside are almost always quite safe. Washington, D.C., Philadelphia, and Baltimore are particularly risky for travelers--they all are worth visiting, but have rough neighborhoods near many popular tourist sites—best to do your research ahead of time and avoid straying off the beaten path. New York, despite what you may have seen in the movies, is actually one of the safest big cities in the country, and you may rest easy knowing that violent crime has become rare in areas frequented by tourists. The main cities of New Jersey are less of a concern, as they are not at all major travel destinations. Bear in mind, however, that Newark, Camden and Trenton are all non-destinations because of their high levels of violent crime.
Mid-Atlantic cities all have increasing gang and drug-related crime. Gangs have moved away from cities like New York City and Philadelphia to mid-sized New Jersey and Pennsylvania cities like Allentown, Reading, York, Lancaster, Harrisburg, Chester, Camden, Trenton, Atlantic City, and Newark. Just be sure to know what neighborhood you're in and be cautious of suspicious activity.
The climate in the Mid-Atlantic part of the United States is not as extreme as in some other parts of the country, but does present perils depending on the time of year. Wintertime can bring ice and snow to inland areas, but only for short periods of time. Summers often are quite humid and steamy, especially in and around the Washington, D.C. area. Fall can bring the occasional hurricane or tropical storm, but these are rare and plenty of advance notice is given.
The upside to staying safe in the Mid-Atlantic is that there is no better place on Earth to develop a brain tumor, get knived, or crash your car—it is home to the best hospitals in the world in Baltimore Johns Hopkins, and the New York City, Philadelphia and Washington, D.C. metro areas. Indeed, the hospitals get visits from the elite of the world, ranging from third world dictators to jet-setting millionaires. If they can't repair you, nobody can.
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As with the majority of the United States, all official signs in the Mid-Atlantic are in English and travelers speaking English should have little difficulty communicating their needs wherever they go. Spanish is widely spoken, mostly by immigrants from Latin America and their families, although the language is also taught poorly to the majority of the native-born population.
Because these five states lie on the East Coast, they were the initial point of entry for most English-speaking immigrants and as such, have retained a much greater degree of diversity in terms of regional accents than the rest of the country accents tended to converge as settlers went west. While you are likely to just encounter General American Pronunciation pretty much wherever you go, you may be treated to a New Yorker accent in Brooklyn, Long Island, or northern New Jersey; Bawlmorese in Baltimore, the baffling -to-linguists Picksburg accent that just keeps diverging ever farther from surrounding accents, a South Philly accent, or southern accents on Maryland's Eastern Shore. You can even find 17th century English accents if you look for them among the isolated island communities of the Chesapeake Bay!