The trouble you'll run into by just connecting a computer to a TNC and to a radio is that the bandwidth is painfully low for anything on the internet.
You can set up a simple packet network and run slow speed stuff. That would be fine for e-mail message type use. You can do that on HF, VHF, UHF, etc.
But really, we are talking about sub-dial up modem speeds. 9.6K.
To do anything useful, you need bandwidth, and lots of it. To get that you need to have several MHz wide channels, and you are not going to get that anywhere other than way up the spectrum. Trouble with that is then the range becomes short and it is 100% line of sight only.
If this is for a hospital, county, city, etc. they already have access to statewide microwave networks for this sort of emergency stuff. They wouldn't necessarily need amateur radio for this. As long as the microwave path is there, they'd be up and running with more bandwidth that amateur radio would be able to reasonably provide. Probably already exists, or they just need to tie into the network.
I'm down in Central California, and I've spent some time up your way. You've got some real challenges if you are trying to get wireless high speed data in/out of there. Anything you'd do is going to require either satellite or microwave shots to the mountain tops and over into another region that hopefully wouldn't be impacted. That's going to be expensive since the mountain top sites are going to need some substantial infrastructure to make them reliable. Battery backup would be necessary, and not just a couple of old car batteries. You'd want routers to do some sort of mesh network, ideally. Weather/fog does get to be an issue, but you overcome that with frequency choice, power and antenna/dish size. I've got a number of microwave links at work and I'm on the ocean, so dealing with rain, fog and weird weather is something we've had to overcome, but most of our shots are a few miles at best.
Having redundant connections using different means would be the way to go. Amateur radio, again, probably isn't going to be your best choice unless you are willing to spend a lot of money.
Alternate fiber paths running north, south and east would be the way to go. I work for a research university, and we've got our own fiber paths running east into silicon valley, south to a connection point about 90 miles away, alternate paths using AT&T fiber, etc. The key is having the unique paths, routers, etc. to make sure you limit the single points of failure.
Something like a DirectTV satellite internet link might be a better choice. Install one at a hardened location, then distribute out from there.
Other choice is the Inmarsat BGAN terminals. Expensive, but will work from just about anywhere. They'll pack away in a case and you just set them up where needed.
Really, this comes down to budget, and unless you have a clearly established list of requirements and a realistic budget, this is just a paper exercise.