There are indeed a few urban gardens in the city. You might have to wait to spring though, to see which ones will be functioning again, or reach out to them. For starters, check out the urban gardens tag to see all related blog posts. It’ll give you an idea who to contact and what gardens the city has had in the past.
The Newburgh Armory usually has plots available and last year there was farming at Downing Park. Also, check out this page. There are a few other grassroot groups who plant on vacant lots they have purchased or have taken over.
I also came across this link today, great tips!
Hope this helps!