Q: Do you get mosquitoes in Barcelona? I am visiting next week and wonder if I need a plug-in repellent for my room?
A: In the summer you may find some mosquitoes in Barcelona however the city generally does not have a mosquito problem unlike many other cities in warmer climates.
As a precautionary measure I would advise to bring a mosquito killer plug-in device to ensure you will be protected in your hotel. You may start finding some mosquitos in May when the weather starts to become warmer, the peak months for mosquitos would be July and August, but there may still be some until November, as the climate is mild here.
In any case, Barcelona does not have a "mosquito problem" and generally you would be fine - you just may be subject to the odd mosquito bite in the warmest months if you are unlucky and for a few euros you can protect yourself against this possibility by purchasing a low-cost plug-in electric mosquito killer.
Outside of the city centre there are areas in the countryside which have more of a mosquito problem due to lakes or woods in the area, but generally, you will be OK in the city centre itself.
Do not forget to put the plugs in your big luggage during the trip when it is a liquid, otherwise you will lose it at the security control of the airport. You can only bring liquids under 100 ml. It is also best to pack the mosquito killer in your hold-luggage as opposed to the cabin luggage to prevent the possibility of security not permitting you to carry it in your cabin luggage.