I am currently in a hotel where "just" a checkbox has to be checked and a button has to be pressed to get access.
I already installed travelmate on my Flint, but after the the Initial interface wizard (I set wwan, wan and 100 there as I do not really know) I had the problem the wifi went down every few minutes but getting a connection and internet. I then disabled travelmate in its options and there was no wifi-down or reboot anymore.
Oh, I think the travelmate cannot handle Portal (HTTP/S) authentication interaction, it is only responsible for WiFi connection or switching, in related documents.
I think you may have to write a script based on the portal page or web interface to achieve auto-login.