Spain

'Best' - for what?
And Menorca is not a city. Neither is it in southern Spain.
And - 'What' 'about a beach city?'

Input of what you want from destinations other than what you can easily find in any travel guide might give you output.

Carmela, have you done any initial research? any initial planning? Please do share it then we can perhaps add suggestions or comments on it.

San Sebastian (known to locals as Donostia) has a beautiful, sandy beach. We were there in rainy November so we didn't spend time at the beach, but it was great to look at. Their aquarium is also worth a visit, and the food is outstanding.

^^ San Sebastian is in northern Spain, at the opposite side of where the OP is headed.

I agree with the earlier poster; we need to know more about your own interests to recommend places. Andalucía is a big region in Spain with lots of things to see and do. Sevilla and Granada are the two most popular tourist destinations and filled with historic sites and neighborhoods. Cordoba is a great small city with the incredible Mezquita and narrow pedestrian lanes. There are places with Roman ruins and quaint hill towns. Valencia is more remote from Andalucía but a great city not often visited by North American tourists. It has a beach area (remote from the city center). The Costa del Sol is lined with sandy beaches and mostly modern resorts and hotel developments. It's a very popular European beach destination. Are you looking for a great beach to lay on or a quaint beach town?

Donostia is the old Basque name - - it came back after Franco kicked the bucket. But, it's a town with a beach, not a beach town.

I grew up just down the coast. The Bay of Biscay is cold. Even as kids we had an acute case of the blue lip shivers after ten minutes in the water during mid-summer.

@Douglas - you got me again - I hadn't seen the "southern" in the original question, but then again, Menorca is east, not necessarily south.

Carmela- on the southern Costa del Sol, Malaga and Torremolinos have beaches. It's a popular destination for Brits escaping the U.K. weather, so you could hear a lot of English, and even encounter pubs with English soccer on the telly!

Carmela, among the cities you listed, Sevilla is certainly top on our list of Spain sightseeing priorities. Granada is a another top stop in that region. Rick's not really in love with any southern Spain beach city, but would suggest taking a bus from Sevilla (5 hours) to the Algarve region of Portugal.

My favorites in Southern Spain were (in this order) Sevilla (because we visited the April fair, otherwise probably number 2), Granada, Cordoba, Gibraltar, Tarifa, Jerez, Ronda, and Antequera (for the passage tombs) and Baeza. I didn't visit Arcos so can't give you an opinion there.

The let-downs in Southern Spain were Cadiz (too run down) and Jaen (a busy city with lots of traffic and few sights).

The best beaches IMO are between Tarifa and Cadiz - the Costa de la Luz. They're sparsely populated and beautiful. Costa del Sol, east from Gibraltar, is one giant resort community.