According to the American Heritage Dictionary, "homogeny" is defined as "similarity of structure between organs or parts, possibly of dissimilar function, that are related by common descent."

"Homogeneity" is defined more generically as "the state or quality of being homogeneous," and "homogeneous" is in turn defined as "of the same or similar nature or kind, or uniform in structure or composition throughout."

The expression "linguistic homogeneity" is commonly used. Take a look at these two citations:

http://www.linguistlist.org/~ask-ling/archive-1997.10/msg012...

"I am currently an undergraduate linguistics major and my highest
interest in linguistics right now is the threat to "linguistic
heterogeneity" (Trudgill, Peter. Sociolinguistics. London: Penguin
Books 1974. pp.187). He also says, "that the disappearance of
languages from the world could greatly speed up the process of
cultural homogenization," (177)."

http://www.surrey.ac.uk/ELI/tavoultz.html

"This study investigates whether there is a systematic relationship between the language attitudes of two groups of third-generation adolescents, descendants of a Greek linguistic minority known as Pontii, toward their mother tongue Pontiaca, a dialect of ancient Greek, and : a) their village of residence , in terms of (relative) linguistic homogeneity, b) intermarriage, that is, their parentage."

Your usage seems quite appropriate to me. In the first instance that you mentioned, depending on what you meant, "homogenization" may be appropriate, IF you are referring to a process, not a state. Otherwise, "homogeneity" is alright.

Fuad