There are loads of cheap hotels in Tumbes  to accommodate the border traffic to and from Ecuador. The very cheapest options, while clean, are unlikely to have hot water or toilet seats, and the mid- to higher-priced hotels have the amenities but not much charm.
Hospedaje Franco (San Martín 105, tel. 072/52-5295, US$6 s, US$9 d) and Hospedaje Tumbes (Grau 614, tel. 072/52-2203, US$5 s, US$8 d) are your best bets for a reasonably clean, quiet room with a private bath.
The plant-lined hallways of Hotel Lourdes (Bodero 118, tel. 072/52-2966, US$12 s, US$18 d) filter into a second-floor sitting room, which looks over the street. Rooms have firm mattresses and are quieter farther away from the street. If this place is full, try Hostal César (Huascar 311, tel. 072/52-2883, US$12 s, US$15 d), with hot water, cable TV, pleasant rooms, and big, clean bathrooms.
About four kilometers north on the Panamericana, outside the city center, is Chilimasa Hotel (tel. 072/52-4555, chili [at] terra [dot] com [dot] pe, US$25 s, US$37 d with breakfast). This is a fairly upscale hotel, with a nice pool for sunbathing and large rooms with cable TV, fridge, and air-conditioning. The location makes it challenging to get back and forth from the center, but big families and tourist groups can make the hotel feel busier than the Plaza de Armas.
The more expensive option is Hotel Costa del Sol (San Martín 275, tel. 072/52-3991, www.costadelsolperu.com , US$61 s, US$72 d with breakfast), on the pleasant and quiet Plaza Bolognesi. The hotel itself is an oasis in this hot, dusty city, with a nice pool, excellent restaurant, and fully equipped rooms with air-conditioning.