Another Solution for Android users to Group Text or Group Message with iPhone users
I'm running the latest version of KitKat on a Nexus 5 and these settings work best for me using the Textra app (not Hangouts).
-First of all you have to be sending and receiving MMS properly first.
-Next, make sure you're using Textra as your default SMS app.
-If that's all working, under the MMS menu in settings check the box for 'Default for Delivery Reports (whether to request MMS delivery reports)' and also check the box for 'Use MMS for Group Chats (MMS can make group chats work better with other smart phones such as iPhones and Android phones)'
-After checking those 2 boxes in the same part of the menu go into 'MMS Settings (Go here if MMS isn't working)'.
-Under that check 'Activate Mobile Data (Set this to temporarily activate Mobile Data when sending or receiving an MMS)'
-Check 'T-Mobile WiFi Calling Fix (Set this to temporarily de-activate WiFi when sending or receiving an MMS. This makes MMS work with T-Mobile WiFi calling)'. Do this regardless of your cell network. I'm on AT&T for example and I needed this.
Under SMS I also have checked 'Default for Delivery Reports' but I think that's unrelated. Everything I've left unchecked.
These settings ensure that group message iMessages coming in from iPhone users come in to Textra properly (over a mobile data connection only, not WiFi). And these settings (if you weren't otherwise connected to the internet) will kick on your 3G (or 2G) just for a moment to receive the group message, as well as kick on for a moment if you are sending a group text to your iPhone friends.
Let me know if this works for you if you have any comments!