Staff is being bitten by our friendly undead vampire moderator, OfTheDamned, and being converted into vampires. They tell me that it has something to do with Halloween, but as a vampire hunter, all I know is that I am going to be very busy!
The easiest way to know if a model is going to give you trouble is to ask us. If we don't know here, then we'll point you at that model's forum for the answer.
If a phone specs out with 4 GB or less of storage (sometimes spec'd as rom or emmc), then it will have a separate, physical sd card and that card will be accessed on the phone through the /sdcard folder and as USB mass storage by a PC.
If a phone has 16 GB or more, around 6 GB will be reserved and the remainder will be located at the /sdcard folder, even though it's not an actual sd card, and you'll need MTP or one of free apps I mentioned to get to it with ICS. Those models may optionally allow an actual sd card in addition. That will be accessed on the phone through another folder, such as /sdcard2 or something, and as USB storage by the PC.
There are a lot of variations out there on the theme, so it's ok and probably best to ask us, model by model.
But you really can't go wrong with ftp via wifi, you can get to everything through your browser and you don't have to sweat the details that way.