My questions are would someone attending Western Rite Church using the Liturgy of St. Gregory, find it similar to to Catholic Latin mass?
What is your Liturgy like?
The simplest answer would be that, apart from being mostly in traditional English rather than Latin, it is almost exactly what one might have found in any liturgically proper Roman Catholic or Anglo-Catholic church or monastery in the years before the second Vatican council.
Are there many converts from Catholicism to the Western Rite Orthodox?
As far as individuals are concerned, there are quite a few, for sure. The already quoted website states that: "inevitably, because we exist in a homely and familiar western liturgical form, disenfranchised Roman Catholics . . . who seek an Orthodox home where they will be welcomed and will truly feel at home, have often found a haven in Western Orthodoxy
". As far as communities are concerned, there is at least one ex-RC WRO parish in the Philippines (and a few more former Old Catholic ones).
What are some of the locations (particularly in Midwest) of some of the Churches that use the Liturgy of St. Gregory?
Christminster, Hamilton, Ontario, Canada. Well, it's not the Midwest but boarders with it.