You will find that many of the Tavira people speak some English (if that is your home language) Learning Portuguese is not simple as the pronunciation of words that look similar to English can be quite complex.
However, your stay will be enhanced by mastering some basic Portuguese words and phrases. So in the Tavira cafe´s it will always help ordering actually what you want.
In towns and villages outside of Tavira itself it is essential to have some rudimentary Portuguese.
Apart from this it is common courtesy to at least attempt to speak the local idiom.
If you are staying for a while we would recommend taking lessons. The language is not easy and it sounds even more complex. The locals speak very quickly which makes it even more difficult to understand. The Tavira locals though are very willing to help so persevere.
A basic introduction to the language can be gained through Transparent Language.
Have a look at this site. We have found it really helps with recognising words and sounds that can seem alien to the English speaking ear.
Ola - Hello
Como Esta - How are you?
Adeus - Goodbye
Não - No
Por favor -Please
Obrigado - Thank you (if you are male)
Obrigada - Thank you (if you are female)