My hotel WiFi has no password. I am using Virtual Box on Linux host with Linux guest. I plan to delete guest Linux VM after browsing.
My main concern is to secure the host OS (Linux) from getting compromised.
Is it safe to use virtual box to browse if I am not worrying about someone seeing what websites I visit or passwords that I enter?
If as you say, you're not worried about someone seeing what websites you visit / passwords you entered, open (without passwords) Hotel WiFi is not a significant factor at all.
In that case, YES. For your main concern, your technique of using disposable VMs for browsing is fairly good security if you are like most people.
It is not enough only if you are targeted by highly resourceful people (like Govt agencies). In that case you should expect that they'll use exploits that escape the guest VM and reach the host VM.
If you want to 'secure the host', just add USB passthrough for the guest, and disable all network interfaces on the host. Then connect a USB wifi dongle to the guest. Verify each interface with tcpdump. On the guest, browse and whatnot. There will be porn.
Also you have to be aware that if you use a nat, the guest will run network through the local interface, bypassing all the firewall rules.
