By 1954, the non-Muslim population of Algeria consisted of around 400,000 people of Spanish Ancestry, making them the single largest ethnic group. However, as 78% of Algeria's non-Muslim population was born in the territory, the vast majority were French citizens.
Keep in mind that most of the immigrants were from Southern Spain, particularly from Alicante and Murcia provinces, but also from Andalusia. Earlier immigrants came from Valencia and Menorca. Prior to World War I, thousands of Spaniards from Southern Spain made their way to Algeria every year (10-25,000) as temporary farm migrants, with most eventually returning to Spain. However, enough settled permanently to form the nucleus of a culturally Spanish community in Western Algeria.
As for the assertion of Argentina being an option, unlike in the 16th and 17th centuries, very few Andalusians emigrated to South America during the 19th and 20th centuries. For instance Argentina's immigrants from Spain were overwhelmingly from Northern Spain, particularly Galicia during the same period. Cuba, which was much like Algeria for Galicians as many went to work on for short periods of time in sugarcane plantations before returning to Spain.
The Spanish-born population of Algeria already numbered 10,796 by 1841, rising to 144,530 in 1886. The Spaniards also were the last large European immigrants to arrive in Algeria with some 12,000 Republicans taken refuge in Algeria in 1939. Keep in mind that by the 1930s more Europeans were leaving Algeria than immigrating due to the better economic prospects in France.