It is never a good idea to carry a lot of money while in Italy or Europe. While the Italian Lakes district is a very safe area, pick pocketing is a common problem in all areas of Europe. Don't carry lots of cash at a time, and make sure it is not easily accessible to pick pockets (the wallet in the back pocket is an easy target).
Traveler's checks are somewhat outdated these days, and a lot of places no longer accept them. Use a credit card; they are accepted in most places and have the best exchange rate. To pull out Euros you can go to Italian ATM machines, known as BANCOMATS. They accept all major debit cards.
Don't forget to alert your local bank that you are traveling to Italy so they don't freeze your account by mistake.
INTERNET AND PHONE SERVICES
Communication to countries outside of Italy is fairly easy these days. Internet cafes exist in all towns and are not very expensive; usually not more than 12 Euros per hour. A lot of them also have phones to make international calls, paying by the minute.
Another option is to sign up with Skype, where international calls are extremely cheap and you only need an Internet connection to use it.
STORE AND RESTAURANT HOURS
Italy is not as convenient as the US in terms of hours of operation for many establishments. Most places are closed in the early afternoon for two to three hours, and also tend to close earlier at night as well. This includes restaurants.
In Italy, it is not the norm to leave a tip. Usually people will leave the change and maybe an extra Euro. The same is true for taxis; don't leave a tip unless you really want to.
Just remember that the customs in Italy and the Italian Lake district are different from those in America. This is just another reason Italian lakes holidays are so interesting and fun!