Here's hoping you won't need to evaluate Boston's reputation for excellent medical care. The greatest threat to your health is the same as in most other North American cities: overexposure to the summer sun. Be sure to pack sunblock, sunglasses, and a hat, and don't forget to stay hydrated.
Whether you choose to invest in travel insurance depends on numerous factors, including how far you're traveling, how much you're spending, how set your schedule is, and your physical condition. For domestic travelers, most reliable healthcare plans provide coverage if you get sick away from home. International travelers should note that unlike many other countries, the United States does not usually offer free or low-cost medical care to visitors (or citizens).
For information on traveler's insurance, trip cancelation insurance, and medical insurance while traveling, please visit www.frommers.com/planning.
Boston and Cambridge are generally safe, especially in the areas you're likely to visit. Nevertheless, you should take the same precautions you would in any other large North American city. Stash wallets and billfolds in your least accessible pocket, don't wave your expensive camera or biggest map around in a dicey-looking neighborhood, and take off your headphones (or at least turn the volume way down) when you're wandering around alone. In general, trust your instincts -- a dark, deserted street is probably deserted for a reason.
As in any city, stay out of parks (including Boston Common, the Public Garden, the Esplanade, the Rose Kennedy Greenway, and Cambridge Common) at night unless you're in a crowd. Specific areas to avoid at night include Boylston Street between Tremont and Washington streets, and Tremont Street from Stuart to Boylston streets. Try not to walk alone late at night in the Theater District or on the side streets around North Station. Public transportation in the areas you're likely to visit is busy and safe, but service stops between 12:30 and 1am. If you're going to be out late, carry cab fare and a charged phone programmed with the number of at least one cab company.
Note: This information was accurate when it was published, but can change without notice. Please be sure to confirm all rates and details directly with the companies in question before planning your trip.