Advances in bilingual research have brought widespread recognition that many aspects of what we previously assumed to be "typical" language development are in fact specifie to monolinguals, and that divergent developmental patterns observed for bilingual children are a normal consequence of acquiring more than one first language. In this chapter, we discuss how studies of sign language bilingualism are poised to effectuate a similar broadening of public consciousness regarding second language (L2) bilingualism, until now built almost exclusively on the study of unimodal speech bilinguals. We summarize acquisition patterns that have emerged from the nascent literature on various sub-categories of sign bilinguals and discuss how these findings affect prevailing assumptions about bilingualism. We argue that more rigorous research on unimodal sign bilinguals in particular is needed to refine our current understanding of bilingual language acquisition and processing, and clarify the extent of critical period effects on L2 acquisition by late-exposed deaf signers.