I don't know about Italy and Spain, but many hotels restrict use of their WiFi or Ethernet service by requiring you to first go to a web page and enter a user ID and password or PIN. This is known as a "captive portal".
Since you are traveling, rather than lug around the extra OBi hardware and a telephone, it would be easier to just use the internet VoIP calling service of your choice, on a laptop, tablet or smartphone. You'd first log into the hotel (or internet cafe's) service, then use a softphone app on the computer to make and receive calls.
If you want to use Google's service, download and install Google Hangouts. Calls
to most phone numbers in the USA are free. If you want people to be able to call you, then you need to sign up for a Google Voice phone number.
Check out the help documents over on the GV site for instructions:
https://support.google.com/voice/#topic=1707989Of course, you could also use Skype, Vonage, or any of the many SIP VoIP providers instead of Google Hangouts.