Will the new perm crown be cemented on better then temp crown? Temp crown has fallen off twice.

Yes in theory, the permanent crown should be cemented on better than the temporary, but it depends on the clinician.  The fit and adhesion rely on a few other factors:  how much tooth height and surface area is remaining above the gum, mechanical retention which is determined by the preparation design - it's good to have some level of resistance when the permanent is pulled or tugged away.  Will the permanent crown be emax, zirconia, porcelain fused to metal, or gold?  Full bonding with resin cement is a great technique to cement, it relies less on surface area and mechanical retention but this is most successful with emax.  The rest of the materials generally require the use of a traditional luting cement that will rely more on mechanical retention.  The chemistry and level of the adhesion is also not as strong as bonding with resin.  Either way, I would suggest 2 common denominators for your dentist to utilize with their technique:  Direct and indirect air abrasion of the tooth and inside of the crown with Aluminum Oxide (this is not however recommended by the emax manufacturer), and cleaning the inside of the restoration with a product called Ivoclean and a proper "primer".  A skilled and knowledgeable dentist will know what these are.  
That being said, there are other factors such as your bite, habits or presence of clenching and grinding, home care and diet which can all have an effect.  A bite adjustment and nightguard might be necessary.  Sometimes, a diagnostic wax-up prototype prior to treatment can be helpful in analyzing the case and to serve as a guide.  This should all be reviewed with your dentist to optimize the adhesion and longevity of the crown.  Hope this helps, good luck!

The cement used for a temporary crown is not the same as for a permanent crown. You shouldn't have a problem with the permanent crown.