US cellphones will work in Aruba. However please keep in mind that if you retain your own US SIM card you may incur considerable roaming fees from your US cellphone company, you should call to see if they offer coverage in Aruba and what it would cost. Consider renting a cell phone or SIM card to use with your own cellphone if your cellphone company does not offer coverage in Aruba. Please also keep in mind that the voltage in Aruba can be as high as 127 volts, so you would need to make sure that your charger can handle this voltage. There are no area codes in Aruba, so just dial the phone number directly without any prefixes. To call the United States from Aruba dial "00" (international prefix to dial outside of Aruba), then dial "1" (international code for the U.S.). and then the area code and phone number you wish to connect to.
More information on Aruba's telecommunication here.