Money and cards...
In Spain the legal currency is the EURO. It will be very difficult for them to accept you to pay in a different currency.
Until 2002, the year the euro was introduced, banknotes from other countries could be accepted in tourist areas, and especially in areas bordering France and Portugal.
Since the existence of the euro, it will be very difficult for them to accept it, and if they do, the exchange rate will be little advantageous. This includes paying
TIPS
If you live in North America, let's make it clear, in Spain tips are much more infrequent, and even non-existent, compared to what you are used to.
In Europe in general there is the impression (and desire) that money is earned honestly through wages, not tips. The worker is already assured of a salary before starting work and will carry out his or her work, with or without tips.
Therefore, the general rule is to tip if the service was extrao