Will all servers work with phpMyAdmin?
PHPMyAdmin is just a GUI/web frontend for MySQL; so you're just after hosting that supports MySQL (ie - most linux packages).
I will have around 11gig of data
Is that 11GB within the database (MySQL) or is it 11GB flat-files?
Only mention it as it's common for there to be database size limits, it doesn't apply to every package but it's worth keeping it in mine.
Will my android app be hosted on the server itself?
The app's APK is handled by Google (or what ever app store you go for); the remote backend data the app needs is hosted and your responsibility.
.....is if I were to upload the files to a free cloud storage server and retrieve from there wouldnt my app just work the same?
Wouldn't even think about it, you'll run into bandwidth issues if the app is even remotely popular.
p.s. how much bandwidth should I aim for? I will be streaming mp3s...
'How long is a piece of string?'
I'd start off by looking at the amount of requested data during a users average session. But you're going to need to sample a big number of users to get any decent estimates out of it.
On past projects we've/i've always ran a closed trial of the app, not only to highlight any issues with the app (you'll always overlook bugs) but it also gives us/me a better idea of backend requirements.
When going live we'll/i keep an extremely close eye on server stats/load and optimise the backend accordingly.
I do question the use of MP3's however; OGG would be a better bet especially considering file sizes and in-turn bandwidth usage (you also want to be reducing the number of audio channels, ie - use mono, where possible).
Similarly i would also be employing some form of caching of the data, especially audio, on the app's devices to reduce backend load.
the android app I am developing is for a charity so I need to keep hosting costs to a minimum if possible...
Not to sound like an a******e but obviously this should have all been sorted (backend providers, specs, costings, contingencies especially how that affects costs) during the specification/proposal stage of the project as it helps with project development (especially when the budget is an issue) but it also saves your bacon from voidable 'client shock' (surprising the client with bad news, usually money/budget/costs).
But as mentioned, look at "cloud" based hosting (AWS, Azure, Digital Ocean - can't say i've used them but they look reasonable, Google Apps/Hosting - again never used it but might be worth looking at) over dedicated hardware for flexibility.
