I think the idea of the mesh network is that various android phones could connect to each other directly (not via the internet which will require mobile data), though at least one will need to connect to the internet to get information from the dash network.
There are many reasons why this will be difficult.
1. The app, to reduce data usage, uses Bloom Filters which means that it only receives data relevant to the addresses in its own wallet. Any other devices connected to this device wouldn't be able to receive any coins. They could send, though.
2. This relates to #1. The app is not a service node and does not keep the blockchain on the device and it does not answer requests from other nodes for block and transaction data, nor does it support bloom filters to devices requesting them.
One way to sort of support the benefit of the mesh network is to have in a particular area, one user who can have a WiFi hotspot on his device that others can connect to or the area has its own internet connection and a WIFI channel. There needs to be a way to connect to the internet to so the miners can mine sent transactions and confirm them.