It's obviously a good idea to learn Spanish if you're planning to move to Spain but it's surprising how many foreigners (especially Brits!) manage to get by for years with little more than "una cerveza y el menu del dia por favor".
The vast majority of foreigners buy into the popular ex-patriate areas where there are large concentrations of their fellow countrymen. The British and Germans lead the way when it comes to buying in Spain and all along the Costas they've established their own enclaves where Brit bars, beer kellers, bratwurst and bingo are all much more in evidence than anything remotely Spanish.
Many ex-pats, especially retired people who have no need to learn the language in order to find work, are quite happy living in a community where there's a proliferation of bars and clubs frequented by like-minded folk from their own country. Life only starts to get tricky when they need to deal with the Spanish phone company Telefonica, the Spanish authorities or Spanish workmen. Still, the die-hard "I'll never be able to master Spanish" ex-pat manages do get round these problems by employing a translator or, wherever possible, labourers and professionals who can speak their own language.
So if this is possible why bother to even attempt to learn Spanish? Let's face it, it's no mean feat for your average linguistically challenged Brit. The simple answer is that even if you only learn the basics of the language you'll find the experience of living in Spain 100 times more rewarding. The Spanish are hugely appreciative of foreigners who attempt to communicate in their language and will generally fall over themselves trying to help if they can see that you're making the effort.
On the other hand Spaniards can be a bit like the Welsh when it comes to overbearing foreigners who expect the whole world to speak English. If you don't even bother to start with a "buenas dias" or an "hola" you might find yourself running up against a brick wall with a Spaniard who speaks perfectly good English but flatly refuses to do so in protest at your perceived arrogance and rudeness.
This doesn't mean you have to master the language to the point of fluency. For most retired people that's virtually impossible as we all know the old grey cells aren't so elastic as the years go by. But get the hang of some basic sentences, take your dictionary and phrase book everywhere, indulge in a lot of smiling and back slapping and you'll be amazed at how far you get in a country like Spain where the people are naturally warm and hospitable.
If you're planning to move anywhere other than the popular tourist areas, learning Spanish will be essential to your survival whether or not you intend to find work. And if you need to get a job, even if it's in one of the most popular ex-pat areas, you'll find a knowledge of Spanish greatly improves your chances of securing employment.