Most hotel restaurants are open to nonguests for breakfast. I recommend the buffet at the Mediterráneo (tel. 07/860-6627, daily 7–10 a.m., CUC15) in the Hotel NH Parque Central .
If all you want is a croissant and coffee, head to Pastelería Francesca (Prado #410, e/ Neptuno y San Rafael, tel. 07/862-0739; daily 8 a.m.–11 p.m.), on the west side of Parque Central  (note that this is a pickup spot for jineteras and foreign males).
The Café El Escorial (Mercaderes #317, tel. 07/868-3545, daily 9 a.m.–9 p.m.), on Plaza Vieja , is the closest in Havana you’ll come to a European-style coffee shop. This atmospheric venue with a Tuscan mood sells croissants, truffle cream cakes, ice cream, and gourmet coffees and coffee liqueurs. It’s a lovely spot to relax.