For web demos, use docker and docker-compose to bring up your entire system on your local Macbook.
For hardware demos, use a big beefy wireless router and your phone as a hotspot to blow through and create your own network.
These days basically everyone has to do demos on the road. Some of us are lucky because they are basically just web demos. In the old days, you would have to make sure the host was running and pray the VCs internet connection is good. But today, I think the best method is to run the whole demo including all the web servers and database servers on a local machine using docker and some sort of orchestration (ansible as an oldie but goodie, bash scripts if you don't have time to mess around or docker-compose for most uses and kubernetes if you already use that).
The advantage is that it is totally self contained and as a side effect, it can be your personal development environment. Most folks are using MacBooks, so the new Docker for Mac even provides a new virtual machine environment although I've found virtualbox/boot2docker work pretty well
If however you have real hardware, then it is tricker, you need to bring your own network with you. Don't rely on what is there because most folks are in very noisy environments. What you want is a super powerful 5GHz router with beam forming to cut through the noise. The Netgear AC1900 Blackhawk is a good one. Expensive but worth the money at $180. The AC1750 is nearly as good at $120.
If you also need internet access, make sure you have a good data plan and bring your cell phone with you. I particularly like the combination of an iPhone on Verizon plus a Google Nexus on GoogleFi. This gives you in effect three of the four big networks. The truly paranoid would also have an AT&T phone as well.