Language
Learning to communicate in Spanish is not absolutely necessary in Costa Blanca and Costa Calida, but it is preferable to make an effort to learn some of the language in order to make things easier when you are with someone who cannot speak much English.
If you are planning to work in Spain, then some knowledge of Spanish is advisable. Even without any formal lessons, you will soon pick up some useful phrases. The language is fairly easy to pronounce and with a little perseverance, you will soon be able to communicate with the locals.
For those who wish to become fluent in the language there are numerous language schools in the region. The local Town Halls run free lessons, although you must sign up for these beforehand as places fill up quickly.