Don't worry about what you read in the press about personal attacks in Moscow/Russia, as they're mostly aimed at someone in particular (unless you've got reason to be aimed at, of course!). Most of what's broadcast in the UK and abroad is just hyped up - for the most part I find living here much safer than in London. Obviously you've got to take due care and attention, as you would anywhere in the world, watching out for pickpockets and don't walk down dark alleys etc. Basic common sense really.
Also, there are loads of foreigners here, so hearing a foreign voice isn't that uncommon, particularly in the centre.
The best time to visit St Petersburg is end May/beginning June during the "white nights" when it's so light throughout the night that you can pratically read a book outside. The whole city gets into a really good mood as well, being the end of the winter, so groups congregrate around the bridges as they're being raised and lowered and in parks etc. Autumn is also a good time, with all the golden leaves - very beautiful.
In terms of the Golden Ring towns around Moscow, the best to visit if you haven't got much time are Sergei Posad and Suzdal. You can do them both in a weekend, but you'd need to go on an organised tour or take a car, as it's quite a drive and best to have a Russian speaker to hand. A good route would be to leave for Suzdal early on Saturday morning, stopping in Vladimir for lunch. There's a lovely church there with fantastic icons and an outside walkway overlooking the flat plains. It's only about 30 mins from there to Suzdal. Suzdal is amazing to walk around, with so many churches in one high street, including a monastery and convent. Stay there overnight (try the convent, if it's not already fully booked) and have dinner in the monastery. On Sunday, drive to Sergei Posad. It's a long drive, but worth it. There are plenty of restaurants on the square outside the monastery, then it's about a two hour drive back to Moscow. A packed weekend, but fascinating and great fun.
Your best bet is to have a good read through a guidebook in advance! I hope you have a good trip!