I wonder why Xfinity does not offer Univision Channel. I am not writing about Univision deportes, just Univision. I emphasize in this because not even the Xfinity agents understand the difference beteween those two channels. Dishnetwork, Direct tv and Uverse offer that channel, the only cable provider that does not offer is Xfinity. I do not know the reason for it, neither have receive a respond from Xfinity.
What area are you from? Univision is a broadcast network, so a local TV station would need to carry it, then have an agreement with Comcast to pass it on. It's possible Dish/DirectTV/Uverse have a special agreement to carry the network feed if there is no Univision station in your area. I'm guessing their web site may have a station locator you can use to check. I don't know Spanish, and don't see anything obvious.
Univision is a local broadcast network, like NBC, ABC, CBS and FOX. Many markets have a Univision affiliate. However, not all do, usually those with smaller Spanish speaking populations.
In some of those, Comcast carries a national Univision feed. In some markets, it even carries this in HD. In many markets outside of where a local Univision affiliate is located, the national feed is available with the Latino packages. In areas where there is a local affiliate, it is in the most basic of tiers.
Some smaller systems in more rural areas lack the Latino packages, which means it's possible that Univision isn't on your system. Requesting it is all you can do in that case. Usually, if Spanish speaking channels are not loaded on to the system, it's believed that there isn't any demand for them in that area.