Flying is the only realistic option for getting to and from Cape Verde. There are infrequent sea services, but they'll probably end up costing as much as a plane ticket. There are regular flights from Lisbon and less frequent flights from other European centres, including Amsterdam, Madrid, Munich and Paris.
Most flights land on Sal, although traffic through Praia is increasing. TACV, Air Sénégal and South African Airways run services from African and North American destinations, including Boston, New York, Atlanta, Johannesburg and Dakar.