If you run a business on the Costa Blanca, your customers probably aren't all searching in one language. Locals search in Spanish; British, Dutch, German and French residents and tourists often search in their own. A site in one language quietly leaves some of those people behind.
Start with who your customers are
Look at who walks through your door, books your rooms or calls you. A restaurant in Torrevieja or a car hire firm at Alicante airport serves a very mixed crowd. A relocation consultant might work almost entirely in English. Add the languages your real customers speak, not every language possible.
Machine translation isn't enough
A translate widget at the top of the page is better than nothing, but Google doesn't treat it as a real page in that language, and the results often read awkwardly. Proper translated pages rank in each language and read as if they were written for that customer.
Tell Google which page is which
Each language version needs its own address, like /es/ for Spanish, and a small piece of code called hreflang that tells Google which pages are translations of each other. Get this right and a Dutch searcher sees your Dutch page, a Spanish searcher your Spanish one.
Keep it manageable
Every language is something to maintain. For most businesses, English and Spanish are the essentials, then add a third or fourth if a real share of your customers speak it. I've built sites in up to five languages, including Casa Tony and QuickNIE.
Not sure which languages you need? Tell me about your customers and I'll give you an honest recommendation.