Pinar del Río has a modest eating scene by Cuban standards — the privately-run paladares are more reliable than state restaurants. Look for places on or near Calle Martí serving ropa vieja, rice and beans, and fresh pork — the basics of Cuban cooking done simply and well.
The local specialty is guarapo, fresh sugarcane juice sold by vendors on the street — cold, very sweet, and cheap. If you want something stronger, rum is easy to find everywhere. The paladares in town vary in quality; ask your casa particular host for the current recommendation, as the scene shifts as licences are granted and revoked.