Vista, California, is in area code +1 760, with overlay code +1 442.
(The plus sign means "insert your international access prefix here." From a GSM mobile phone, you can enter the number in full international format, starting with the plus sign. The most common prefix is 00, but North America (USA, Canada, etc.) uses 011, and many other countries use different prefixes.)
Chula Vista, California, is in area code 619, along with most of the city of San Diego.
Mar Vista, California, is in area codes 310 and 424 (overlay).
Martinez, CA, is in area code 925.
Victorville, CA, is in area code 760 and overlay code 442.
The area code for North Highlands, CA is 916.
San Clemente, CA, is in area code 949.
The country code for Paraguay is +595, and the area code for Bella Vista Norte is 038, which is +595 38 in international format.
The country code for Paraguay is +595, and the area code for Bella Vista Sur is 0767, or +595 767 in international format.
Cordelia, California, is in area code 707.
Cambria, CA, is in area code 805.
Petaluma, CA, is in area code 707.
Hayward, California, is in area code 510.
Concord, California, is in area code 925.