Well when someone did organized a protest ride called critical mass a few years back but only a handful of people showed up. I joke to this day that we were critical, but we were no mass. The ride that is referred to in the picture is the Downtown Highlife bicycle ride. It's less of a protest and more of a fun ride which meets at the Alamo every last Friday of the month at 9pm.
If you're really angry and really want to make a point, I would avoid making the same mistake with the critical mass ride. Instead, might I recommend that you crash the Walk & Roll rally that is held every May.(Image 52.1) This event will take place Friday May 6, 2016 at 8AM. This event celebrates the action taken by the city to encourage walking, biking and riding VIA. But as I wrote two years ago in the posting San Antonio isn't Serious about Bicycles, this event is simply a lie.
So if you choose to make a point, I recommend the following signs in the memes below. Please inform me that your doing this, I'll be happy to spread the word. And If I do manage to show up, I'll be carrying this image (Image 52.6)
52.1: The official Walk and Roll Rally. More info can be found here: https://www.facebook.com/events/1686470051592907/
52.2: The FB conversation that I'm referring to in the post.
52.3-52.6: Memes that I recommend that you download and/or make similar protest signs.