Taking "glottalization" to mean "pronounced with closure of the glottis", the glottalization of the voiceless stops p/t/k before another consonant is quite general in midwestern English and some other dialects. This is not necessarily a conversion to glottal stop, though, since that requires also a loss of the oral closure. A glottalized t' can lose the alveolar closure to become just a glottal stop, in my midwestern speech, when at the end of a syllable and before another consonant other than "s". Glottalized p' and k' (and t') can lose their oral closure to become just a glottal stop before a following homorganic consonant (meaning a consonant at the same place of articulation). So, for instance, I have glottal stop in such phrases as "pick grapes" or "stop marinating", where the development is, first, "pick' grapes" by glottalization, then "pi? grapes" by loss of oral articulation. Evidently, the oral articulation is merely delayed in these cases.
I think there is a whole book about a similar phonological development in Britain, by Eleanor Higginbottom (sp?).