Reliable router for a hotel

For about 100 clients accessing the internet I'd not use any home-products. A Cisco 800-series router will do fine though, and is also fairly easy to set up. New, they cost around $300-$400.

That is correct, you probably won't go much above 20 users simultaneously excepting occassional peaks. But what you don't want is for the router to bog down due to the amount of connections, or in extreme cases restart.

If you know IOS, there's a lot you can do with the 800-series to secure the customer's network without an additional firewall (although it doesn't completely replace it).

I'd recommend buying the version with pre-installed IOS for Advanced IP services, as the other two versions have 28 Meg flash cards, and the adv IP has a 32 MB flash card. You can always download the adv security from Cisco and install it.

Tbh, I'd avoid anything Motorola. In my experience motorola still has a long way to go concerning routing software, and I can say that with a certain confidence as my employer (unfortunately) has bought a lot of Motorola equipment. Which only works thanks to extensive work-arounds.

The Cisco 800-series are proven routers and are extensively used is like environments.