I have never messed with fresh flowers on a wedding cake.How do you go about working with them as far as touching the cake? wouldnt they bleed onto cake?

Depends on the type of flower. Some flowers do leak out a type of sap when they are cut- an example of this would be gerberra daisies. But usually if you cut a flower and let it sit touching the air for a minute or two the sap will seal up the cut before placing the flower on the cake.
Now as far placing the flowers on the cake, the matter in which you do it will depend on your comfort level. I have always placed rinsed and non-rinsed flowers directly on the cake and no one has yet to complain about getting sick. Some people say that you should put some type of barrier between the flowers and the cake. Whether it be a separator plate, a flower spike, saran wrap, etc. Some people say you should only use organic flowers, some people feel comfortable enough to use non-organic flowers from your local florist. If you are going to use flowers straight out the garden- whether it be yours, the brides mother's, the neighbors, etc- make sure to check for bugs first. When you buy flowers from a florist- who usually has things shipped in- most of the bugs that may have been in the flowers has either been killed off with chemicals or they died in the shipping process, or the cold air from the coolers that flowers are stored in has killed them.
**Note- there are not too many steadfast rules as to what is considered organic by the US government, some organic things may still have had a pesticide used on them.
Again- how you use the fresh flowers is up to you and how comfortable you feel.

Thank you so much now I know alittle about what to do