Forex is like any other business there are trustworthy people and people who are not so trustworthy.
However there are things you can do to protect yourself if you are thinking of joining a signal service. Firstly you need to find out what kind of signals they provide. Some provide short term signals that are taken from the fifteen minute to the hourly chart. Whilst other are longer term signals taken off the four hour or daily chart.
They are very different services, with the shorter time frames you will get a lot more signals, however they will not be as strong as the signals that are generated on the four hour charts or daily charts.
Things I would look for are, If the site had a trust logo and if they offer a money back guarantee. If they do its a no brainer because its’s risk free.