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I answer from Madrid, I'm 59 and know most of places in Spain, included Islands. If I make a mistake in written English, please tell me where.

Adamina: I presume that you can think that Spain is everywhere almost the same kind of land, or climate, or society. It can be true thinking on Germany or France, but not valid for Spain, although with similar size. You have the green and rainy country in the Northern part, the continental climate in the Central regions, and the warmest and sunny places in the Mediterranean. With exceptions. And people live according to climate.

Avoid crowded places in big cities, if you carry your precious belongings with you. There are some foreing people, most of them from eastern Europe, and some locals as well, that use to live on your money, if you are clueless.

Mallorca, the bigger Baleares island has a portion at its Nord that is different to the rest. Tenerife, the biggest of Canary Islands, has both tropical climates: dry in the South and rainy in the Nord, because there is the biggest mountain in Spain: the Teide Vulcano.

Then, if you prefere, as most of cold climate's visitors, to be in a good an warn beach 17 hours a day dont dobubt, Mediterranean, Balearic or East part of Canary Islands. If you come in Spring-Summer and wants to know most of Spain, you can discover not only the most touristic sites, but you can go to relatively quiet places and discover history, people and pleasure. You must use airports to go to Islands: 1 hour from Madrid to Baleares, and 3 hours for Canarias. Trains can be a good travel solution to some cities but between small cities, bus is usually better. Spain is not a cheap country now, but not at the level of Paris. To find a hotel is not a problem in any place.

But dont forget that in Spain you can travel 100 km and traverse sometimes two or three very different kinds of land, architecture, and living style. For example, you can be on the snow in the bigger peninsula mountain: Sierra Nevada, and in two hours by car, being in the most sunny beach.
Look at Earth Google and see photos of different parts, not only coasts. Don't forget that Portugal is always near us, as well.