Spain is very safe for tourists. Pickpocketing is the primary concern in major tourist zones — Barcelona's La Rambla and metro system have a particularly bad reputation for bag snatching and distraction theft. Use anti-theft bags and split your cash.
Nightlife is vibrant and safe; Spanish cities tend to be lively late into the night with large crowds even on weekdays. Health emergencies are covered under EHIC/GHIC for EU/UK citizens. The emergency number is 112.