It entirely depends on your reaason for growing Sarras, If for seed then no, leave the flowers (here is where I disagree with linuxman ((Sorry) no plant 'energy' is a waste) even if your plants provide you with but a few viable seed in the first few years, the annual routine (in my opinion) will help to condition your plant into providing better seeds annualy as long as they are well cared for. If on the other hand you wish to grow your Sarras for thier immediate size, shape, colour and are unconcerned about future possible hybridation then as previously stated, cut those flower buds and allow the plant to utilise its annual energy hype to go towards imediate plant 'looks'
Besides as linuxman stated, the flowers are so incredible why cut em off ???
I remember my first ever produced Sarra flower, I was so gobsmacked at its exotic beauty I took gigabytes of pics and stll have them all to this day !
Hybridising living things can often produces examples that may find difficulties living in the natural world without ongoing help from man, I leave it to your morality, expertise and commmitment as to decide thier future.