Ask any Spahish person and, like people everywhere, each one will probably tell you his or her home town is the best place in the world!
But if you want a big city, you could look at Valencia. It's the third biggest city in Spain with over 800,000 people and is on the coast with nearby beaches and a big port. It has a large old centre full of historic buildings, museums, a famous university, beautiful streets etc. The food is also very good - the paella is especially recommended. As for living and working there, all cities in Spain have an unemployment problem now of course, and Valencia does too, but it is a big industrial and tourist area and there are still some opportunities.

If you prefer a smaller city, Alicante, further south on the same eastern coast, is another beautiful and historic place but less than half the size of Valencia.