Coffee and bananas dominated the Central American economy after the turn of the century, accounting for 75% of the region's exports in 1930. Central America became very dependent on the fortune of their exports. Did they have any other resources or product to export if other countries were unwilling to purchase coffee and bananas, as these were classified as luxuries?
There is also Sugar Cane, which grows well in tropical wet areas.
Assuming you don't count Mexico, Central America is primarily tropical jungle (with a bit of wet highland areas, good for growing coffee). Not many people ventured into the jungle interior. Even today with modern tools and methods, efforts to exploit the resources in jungle areas tend to start with burning down the jungle. The prevalence of tropical diseases from Africa made the situation even worse.
The USA's successful effort at building the Panama Canal transformed things a fair bit. For one thing, trans-shipping activities would have boosted the local economy of Panama at least. For another, during the effort the causes of a lot of tropical diseases were discovered and disease-control efforts were perfected, so they were never quite the same bugaboo as they were previously.
The area does have some gold deposits, and there were even at the time you mention some efforts to exploit them. However, economically they don't seem to deserve more than a side mention in any sources I could find.