I've been down to Guatemala several times in the past few years--my daughter lives there--and have also spent a few days in Honduras. You should have no trouble sticking to a $30 a day budget for those two countries...Costa Rica is pricier, but have no direct experience. A good way to cut costs on lodging is to travel with a friend...a double room is usually the same price as a single. I've stayed in many hotels of the $5 a night variety...they are usually fine, but check the room and the bathroom before committing yourself. Price of food is not really an indicator of its quality or safety. Meals in markets are often good because the food turns over quickly. A trip to the bakery for breakfast and/or supper also saves on meals. Then get a fixed price lunch and you're set. Unless you're drinking a lot of alcohol, or travelling on guided tours, you should be able to get by for $15 a day in many places. Hope this helps a bit!
People always mistake South with Central America for some strange reason. I was there from Nov 05 to Mar 06 and did Belize to Costa Rica ...
i lived in:
Belize for $20/day
El Salvador ... my family comes from there so i hardly paid for anything but i would say its a big more expensive because less tourist so about $20/day probably cheaper if you stay at La libertad (surfing spot).
Honduras $15-20 / day .. more expensive in Roatan but you can always manage to find a place that has a fridge and make your own food.
Costa Rica $20-25 .. more expensive, lots to do .. plenty of National Parks .... i really enjoyed Costa Rica spend a month there, reason why i never made it to Panama ...
i found Guatemala to be the cheapest for everything, same for tours and things to see ... i only took local buses, stayed in cheap hostels or pensions ... and ate on the street...i did get really sick in Guatemala from something i ate but after that my stomach was set and never again since then ive had a problem.
I had a great time in Central america, really enjoyed that forgotten part of the world... probably cheaper also to travel with someone else because of where you stay ... there was a really cool hostel in Rio Dulce (guatemala) that was $2/night. i cant remember the name but there is only one, its also an orphanage.
place i enjoyed ... antigua (guatemala) granada (nicaragua) all of Costa Rica (Santa Teresa was just out of this world) ...
oh and by the way ... there is no charge at the Guatemala border just be careful, the officer will tell you otherwise ... Honduras is $3 .. El Salvador $10 .. Nicaragua $7 and free for costa rica.
hope this helps ... carol