Documentation jumps from 1 node to 3 nodes.
I'm wondering if two nodes would work fine, so I can have one on each side of the globe just for redundancy should a colo or hypervisor go down. We only have ~250 users, so i dont really need 3 nodes to support 2000 users at this time
Yes, you can only run 2 nodes in Data Center, so no concern there.
To Tiago's point, you need low latency between nodes so you can't have them across data centers that are that far apart. AWS is a little different in that they support multiple Availability Zones within each Data Center and you can have your nodes separated in that respect.
The one exception is Bitbucket Data Center which has a concept called Smart Mirroring. This allows you to have a read only node anywhere in the world that allows local teams to pull their repositories much more quickly. You still commit to the core node cluster for your writes, but that's a much less data transfer intense process.
Data Center does not support multi-geo clustering; all nodes must be in the same physical location. However, customers deploying Data Center on Amazon Web Services have the choice of having their application nodes span multiple AWS Data Centers within the same region (https://goo.gl/fC1WdA).
Hope this helps. Cheers,Tiago