Q. What is a traffic bouncer, is it safe?

Bouncer is just another name for a proxy, a proxy that serves a particular end, such as FTP or IRC bouncer. A common bouncer is an IRC bouncer, where software like ZNC allow you reflect your traffic, bounce it, through another IP address, avoiding exposing your own home/origin address.

An FTP or Web traffic bouncer does the same to avoid network traffic congestion. Some ISPs will run their exchange points hot (filled to over 50% capacity), in particular those exchanges that handle the bulk of their trans-oceanic traffic. Historically this has included Comcast in the states, and Shaw in Canada. A bouncer, is a proxy, usually with an uplink to a quality backbone, such as Level 3 - by using that proxy, you bypass the the ISP's self inflicted congestion at their exchange point at get better speeds.

In highway traffic terms, it is an interstate bypass loop, where you are able to avoid the congestion say, found in a big city it is looping around.

It is a not uncommon way to speed what would be otherwise slow traffic. How effective it is more dependent on your ISP, and how congested the bouncer is at any particular time. Depending on the traffic they can be expensive.

Speed testing, and using MTR, the ping trace route tool, can tell you if it works for you.

As to being safe, bouncers by definition just bounce the traffic, if the traffic is secure coming in, it will be securing going out.