Serial works well with all USB to Serial adapters based on the Prolific PL2303 chip, even if you are running El Capitan.
However, you may run into problems if you have an outdated or incompatible driver installed on your system. If you're using an incompatible driver, the most common symptom you'll experience is the device seems to open okay, but no data can be sent or received. Other, less common problems increase in severity all the way up to a full-blown kernel panic, which crashes your entire computer.
If you are having trouble, open the Settings panel and click on the Device Info tab. If you see you're using the "Built-In" driver, you are using Serial's built-in support and the problem may lie elsewhere. If you see you aren't using the "Built-In" driver, however, you may want to remove the driver to see if that fixes the problem. Instructions on removing a third-party driver may be found here: How do I Remove an Incompatible Driver