Crossing the Nicaragua border (border crossing at Peñas Blancas) at this time of year takes some patience.
If travelling by bus allow for about 2 hours (1 hour on each side of the border). The process involves about 30 minutes or less checking out of Costa Rica and 90 minutes or more checking into Nicaragua.
At the Costa Rica side it is only a matter of presenting your passport (or other travel document), while on the Nicaragua side it is a matter of customs (this takes about an hour) and then checking in.
Bus companies usually collect passports and do the stamping thing. On the Costa Rica side it has to be done personally, on the Nicaragua side you will be handed back the document by an immigration official.
If by car and you have all the paperwork – MOST IMPORTANT IS THE EXIT FROM COSTA RICA PERMIT – calculate about 30 minutes on the Costa Rica side (coming or going) and about 2 hours on the Nicaraguan side (coming and going).
The exit permit is obtained only from the Registro Nacional, which is closed until January. Most of the time on the Nicaraguan side is spent to find an official to inspect the vehicle. In addition, you will need to buy road insurance, pay one tax after another. In total there area about a half dozen people involved in the process of clearing your car into Nicaragua. The same occurs on the way back to Costa Rica. And then there is the personal checking in and out with immigration and customs.
Crossing into and out of Nicaragua with a vehicle is not for the faint at heart!
If walking across the border allow between 30 and 60 minutes. Most of the time is taken up waiting in line on both sides. If you can, avoid arriving at the border crossing during the same time the buses arrive. Best to get there a few minutes before, or enjoy a nice cold one waiting for the buses to clear. Not so bad on the Tico side, a madhouse on the Nica side.
PS. Foreigners entering Nicaragua must pay the “visitor” fee both to enter and then to leave. No cost to leave or re-enter Costa Rica.