American Airlines have round trip airfares travelling from San Diego (SAN) to Barcelona Spain (BCN) for $455, making 1 stop. These are main cabin, regular economy fares.
Departs SAN: Jan 19-20, 22-26, 28-31; Feb 1-4, 25-27; March 5
Returns: good availability returns, typically 7-10 days okay
Enter travel information on known and reputable OTAs such as Expedia [expedia.com]
to book. Bundling hotel with airfare will save money.