The only con to getting your phone unlocked is that it costs money to do, if you get it done officially through Bell. As stated before, it simply allows you to use a different provider's SIM card. When you return home, you put your Bell card back in, and continue with no change at all, reverting to your Canadian phone number and service.
In Spain, if you get the Vodafone International SIM card for tourists (Euros 15) it does not include text messages. If you add on some prepayment, you can text but the messages are quite expensive. Instead, since you will have the data service, you can "text" with Facebook messaging or WhatsApp, or even use email. When you put the Spanish SIM card in, all of your accounts like email and Facebook will work as normal. Only your telephone number changes.
My suggestion is to get a Spanish SIM card with at least 1 GB of data, and arrange with your partner to communicate by Facebook messaging or WhatsApp or even email. You will receive those messages right away because you have data with your cell coverage. You don't need the SMS text messaging to your phone number.
Depending on where you plan to start, you may have a few days before you get the new SIM card. Be sure to turn OFF data roaming and rely on wifi. If necessary you can still use your phone at whatever rates Bell charges per call minute and per message. (I think Rogers charges me $2/minute and $.75/message. That is fine for "emergencies" but can get expensive if used a lot.)
I hope my explanation is not too confusing!