This is from the website of the World Health Organization about Typhoid:
There is a higher risk of typhoid fever in countries or areas with low standards of hygiene and water supply facilities.
Risk for travellers
The risk for travellers is generally low, except in parts of northern and western Africa, in southern Asia, in parts of Indonesia and in Peru. Elsewhere, travellers are usually at risk only when exposed to low standards of hygiene. Even vaccinated travellers should take care to avoid consumption of potentially contaminated food and water as the vaccine does not confer 100% protection......"
Costa Rica does not have "low standards of hygiene" as previous visitors can assure you.
If it makes you feel better, just drink bottled water - but it's a waste of money. The only caution I would give you is this: Don't drink river water.