You cannot cross into Nicaragua with a rental car. You can only do so with your own vehicle. If it has Costa Rican plates, you’ll need a special permit from the Registro Nacional (tel. 506/2202-0800). It’s good for 15 days and must be obtained in person from the main office in Curridabat, San José (there’s also a Registro Nacional in Liberia).
Visa requirements are always in flux, so check in advance with the Nicaraguan or Panamanian embassy.
Citizens of Canada, the United States, and most European and Central and South American nations do not need visas to enter Panamá. A tourist visa is issued at the border ($5, good for 30 days).
Paso Canoas: [1] The main crossing point is on the Pan-American Highway. The border posts have been open 24 hours, but hours are subject to change (at press time, they were open 6 a.m.–10 p.m. daily). If you don’t have a ticket out of the country, you can buy a Tracopa bus ticket in David to Paso Canoas and back. A bus terminal on the Panamanian side offers service to David, the nearest town (90 minutes), every hour or two until 7 p.m. Buses leave from David for Panamá City (last bus 5 p.m.; seven hours). Panamanian border guards may require proof that you have a ticket out of the country; there have been reports of disreputable guards at Paso Canoas causing problems for tourists. It’s best to buy your return ticket in advance in Costa Rica.
First, get a Costa Rica exit visa from migración (tel. 506/2732-2150) by the Tracopa bus terminal 400 meters west of the border post, where you can buy your Panamá tourist card. No rental vehicles are permitted, and private cars are usually fumigated ($5). Still, it’s very easy to accidentally drive through this border post without realizing it. The post is crowded, confusing, and has no barriers. I’ve done it twice, and no one stopped me. Simply turn around and drive back!
Sixaola: [2] This rather squalid village on the Caribbean coast sits on the north bank of the Río Sixaola. Its counterpart is Guabito, on the Panamanian side of the river. The two are linked by a bridge. The Costa Rican Customs and Immigration offices (tel. 506/2754-2044, 7 A.M.–5 P.M. daily) are on the west end of the bridge. Panamá is one hour ahead. Hence, the Panamanian office (tel. 507/759-7952), on the east end of the bridge, is open 8 A.M.–6 P.M. daily.
Minibuses operate a regular schedule from Guabito to Changuinola (16 km) and Almirante (30 km). Taxis are available at all hours to Changuinola ($8), from where you can take a water-taxi to Bocas del Toro ($5) or fly or catch a bus onward to the rest of Panamá.
Río Sereno: There’s another crossing between Costa Rica and Panamá, at the remote mountain border post of Río Sereno east of San Vito, in the Pacific southwest. The Costa Rican Immigration (tel. 506/2784-0130) and Panamanian Immigration (tel. 507/722-8054) are 50 meters apart and open 8 A.M.–5 P.M. daily.
Río Sereno: There’s another crossing between Costa Rica and Panamá, at the remote mountain border post of Río Sereno east of San Vito [3], in the Pacific southwest. The Costa Rican Immigration (tel. 506/2784-0130) and Panamanian Immigration (tel. 507/722-8054) are 50 meters apart and open 8 A.M.–5 P.M. daily.
Southbound, Tracopa (tel. 506/2221-4214, www.tracopacr.com [4]) express buses leave from Avenida 5, Calle 14 in San José for Paso Canoas daily at 4:30 P.M. and for David in Panamá at 7:30 A.M. and noon ($9, eight hours). It also has slower service to Paso Canoas at 5 A.M., 1 P.M., and 6:30 P.M. Northbound, Tracopa express buses depart David at 8:30 A.M. and noon.
Ticabus (tel. 506/2248-9636 reservations, tel. 506/2223-8680 terminal, www.ticabus.com [5]) buses depart Avenida 4, Calles 9/11 in San José for Panama City daily at 11 P.M. (executive, $37) and noon (regular, $26). Return buses (tel. 507/314-6385) depart Panama City at 11 A.M. (executive) and 11 P.M. (regular).
Transporte Mepe (tel. 506/2257-8129) buses depart the Gran Caribe terminal in San José for Sixaola and Changuinola daily at 10 A.M. (eight hours, $10). Return buses depart Changuinola at 10 A.M.
Links:
[1] http://www.moon.com/destinations/costa-rica/golfo-dulce-and-the-osa-peninsula/ciudad-neily-and-vicinity/paso-canoas-crossing-panama
[2] http://www.moon.com/destinations/costa-rica/the-caribbean-coast/rio-sixaola-region
[3] http://www.moon.com/destinations/costa-rica/south-central-costa-rica/buenos-aires-and-vicinity/san-vito
[4] http://www.tracopacr.com
[5] http://www.ticabus.com