Hi, I have little idea how much internet bandwidth a mining rig requires. Does it vary greatly between a 6 GPU or 13 GPU rig ?
For 12 rigs in front of a 16 port Switch, is a 100Mbps Switch fine or should you go for 1Gbps ?
10 MEGAbit is plenty to handle tons of rigs - latency isn't a significant issue at ETHERNET SWITCHING speeds, your latency via the Internet to the pool is going to be thousands of times higher, and the bandwidth usage is SMALL.
Avoid wifi - it's NOT nearly as reliable as a good Ethernet wired connection.
With that said, Gigabit is cheap enough any more there's no point in going with less and it's got a lot more room for future expansion - unless you get the 100 Megabit gear DIRT cheap and it's good stuff like 3Com, Cisco, or Netgear "Blue Box" professional gear.