Some podcasts you can download and store in advance. That means you can download them via wi-fi and not have to use online data. The podcast's I subscribe to are basically streaming podcasts ( AFAIK ) so I have to use on-line data to play them while on the bike. I have a number of songs stored on my phone so I don't need to stream if I don't want to. I also have audible books stored on my phone too although at the time I don't have anything new. I think you're right, I don't think streaming "audio" is going to kill my data but it's not the ideal situation.

If I'm going to use something like a speaker on my bike I'm usually riding at night so there is generally not a lot of passing traffic or highly distracting ambient noise. That said heavy traffic is always going to be a factor regardless of what type of speaker you are using. That and just the fact that air is swishing pass your ears so there is that noise to deal with as well. The only downside to the one I bought is that it doesn't have a port for using an MP3 type USB chip. I knew that when I bought it but since I won't be using one of those I just didn't care. Last night I was using full finger gloves because it was cold and it was hard to operate both the speaker and my phone unless I took a glove off. Oh, and FWIW, even with the music playing at full volume I could always hear the approaching traffic, at least on the faster roads. Riding at night can be somewhat boring because there's not much to look at if you catch my drift. Having some music to listen to at night helps to give my mind something to focus on rather than just looking at the beam pattern in front of my bike. I doubt I'll use the speaker for day rides but heck I suppose it will depend on where I'm riding. If I'm using RWGPS to guide me on a ride I doubt I'll be playing music.