This variationist study compares the extension of estar in contexts where normatively one would expect the use of the ser, in the Spanish varieties spoken in Sonora, Mexico and Arizona, United States. An analysis of 1,582 tokens in 36 interviews shows an overall innovative use of estar of 16.2% in Sonora and 20.8% in Arizona, percentages comparable to previous studies. Place of origin of the speaker (Sonora/Arizona) is not statistically significant and the distribution of the factors is very similar in the two communities, suggesting bilingualism (Spanish-English) does not result in an accelerated innovative use in this corpus. A discussion of previous research also provides evidence against a general tendency towards an accelerated use of innovative estar as the result of Spanish-English bilingualism in US Spanish. The methodology implemented in this study (comparing Sonoran monolinguals and Arizonan bilinguals from Sonoran families), provides a needed control when discerning between contact-induced change and language-internal dialectal variation.