That's a great and practical question! For a standard one-block long park, I'd generally recommend starting with 3-4 outdoor trash cans as a solid baseline. Here's my reasoning, which considers both visitor convenience and park maintenance.
Think about key activity points. You'd ideally want one receptacle near the main entrance or a central gathering spot, like a bench cluster. Another should be placed close to any playground area where families generate snack wrappers and drink containers. If there's a dedicated picnic table or a sports court, that's a prime location for the third. A fourth can, perhaps midway along a walking path, serves those strolling through.
The goal is to have a bin within sight or a short 30-second walk from any point. This "convenience radius" discourages littering. The exact number can flex based on your park's specific features, foot traffic, and local wildlife concerns (like raccoons, which may require secure, animal-proof bins). It's always better to start with a slightly adequate number—you can always adjust later based on how full the cans get and user feedback. Well-placed, regularly emptied bins make a park more enjoyable for everyone!