The official currency of Cape Verde is the escudo, abbreviated CVE and indicated with a cifrão a symbol similar to the dollar sign, but with two vertical strokes instead of one after the amount. The currency is fixed against the euro at 110$ per euro.
In the resort islands of Sal and Boa Vista, euros are commonly accepted, although you might receive change in escudos.
Money can be changed from all major currencies at the international airports at Sal and Praia. Bank branches at larger towns will also change money. Larger towns also have ATMs that will take Visa, MasterCard and Maestro.
High end hotels will accept credit cards. Other hotels will expect cash although many mid-range ones will accept euros at a reasonably exchange rate slightly worse than the banks. For everything else, expect to pay in escudos.