You might be allowed though to play the 2
opening as 2-way, either
strong, game force or
weak with diamonds.
Partner will respond 2
whenever he doesn't mind a pass.
Whether this method would be allowed depends on where you are and the "level" of this method.
In the UK, many multi bids are allowed with both strong and weak options at level 3 (I think) so my guess is that this convention would be that level. No doubt you'll use 2
for some other purpose eg also a multi (weak 2 in either major possibly with a strong option) or as flannery. If you play it as the multi then your 2
bids would probably be "tartan" (5 cards + 5 in lower ranking suit) or possibly a strong bid.
Why it is important for me to list these variations of the other bids is so that you are sure to check the "level" of those bids too before you employ them.