The golden rectangle is between Calle de Fuencarral and Calle de San Bernardo — close to two metro lines, every café worth queueing for, and Gran Vía at the bottom of the hill. Rooms directly on Dos de Mayo or Calle del Pez are in the thick of the weekend noise; Calle del Espíritu Santo and the streets uphill toward Conde Duque are calmer.
Malasaña lists around 190 bookable hotels and guesthouses, from roughly €42/night. Prices on the area page are live; booking 3–6 weeks out usually lands the best rate, with free cancellation on most rooms.
If it books out or you want to compare: Chueca (from €46/night), Gran Vía (from €48/night), Chamberí (from €52/night) — each with its own area guide on this site.
Curated picks are coming — meanwhile, the live search covers every bookable property at the same price or better.