By law you are expected to carry some form of photographic identification at all times, such as a passport, national ID card or driving licence.
The blood alcohol limit for driving in Spain is 0.05%. There are stiff fines (up to €1000) for anyone caught exceeding this limit. Levels of 0.12% and above carry a risk of imprisonment.
Cannabis is legal but only for personal use and in very small quantities. Public consumption of any drug is illegal.
If arrested, you will be allotted the free services of a duty solicitor (abogado de oficio), who may speak only Spanish (and Mallorquin). You are entitled to have the nature of the accusation against you explained in a language you understand, and to make a phone call.
If you end up in court, the authorities are obliged to provide a translator.