Here is what I had to pay when I entered each of these countries (July 2009).
Guatemala: ~$1 (I forget exactly)
El Salvador: free (and they don’t even stamp your passport)
Nicaragua: $10 [$7 to enter with lots of paperwork, then $1 to enter the border area in Sapoa at Costa Rican border (weird), then $2 to exit the country, paid only in Cordobas or US Dollars (so don’t change your money until you get to the other side – I made that mistake)]
Costa Rica: free (but long lines at Penas Blancas, coming from Nicaragua)
Panama: $1 (for a stupid passport sticker you buy from an unofficial-looking guy who hangs out by the immigration area, but apparently you need it)
You get 90 days of travel within the four countries of “centroamerica:” Guatemala, El Salvador, Honduras, and Nicaragua.
I set my bike against the railing of a small bridge and wandered down to pee. Mid-stream, I heard a rattle on the road. My helmet, which I had set on the back of my bike, had been blown off and into the road from the rush of a passing semi-truck. I rushed to the road and saw another truck coming. I signaled for it to slow down. But it didn’t, and I saw my helmet go dancing underneath. The damage was bad. Two large cracks on both sides, and small ones in the front. I’ve had it for over three years now, and I didn’t want to lose it to something stupid like this. At least it was all in one piece. I’ve been wearing it anyway since it’s better than nothing.
Antonio and I cut through the skinny, mostly flat section of Honduras in two days, although we got delayed in our Choluteca hotel watching the endless men’s Wimbledon final (which ended Federer 16-14 in the fifth set).