There was a huge rise in terrorism against westerners in Saudi after 9/11 and the invasion of Iraq. Compound bombings, shootings and the kidnapping and beheading of American Paul Johnson.
That all being said. If you go with percentages it is still a safe country, you need to take precautions like anywhere else. The country is much safer now since King Abdullah came to power in 2005. It is a very different culture and an experience you will never forget. You have to weigh the risks. Your biggest risk in Saudi is not the terrorist but the average Saudi driver. The accident death rate is 25 times of that in the USA. That is one reason they need paramedics so badly.
Saudi is a chance to see and live in a culture that is thousands of years old, hisorical sites and mostly friendly people (except when they drive). I would not trade my time in Saudi for anything.
Use common sense and caution. There are places in LA alot more dangerous than most of Saudi. Again I recommend the book "Paramedic to the Prince" a very fair and balanced view, by a medic who spent ten years there. If you go, keep an open mind.....