If you know the layout of your blocks, pressing them in advance would be quicker. You can also just leave them as is. In my experience, there are some patterns where having alternating seams is impossible.
And Mom, pressing seams open is totally acceptable. I've made many patterns, especially modern quilt patterns, where the instructions call for pressing seams open. It's a matter of choice, and I think it's certainly better than having two seam allowances going the same direction. It does take a lot longer, which is why I avoid it if possible.