New to triathlon and want to race soon

I am new to triathlon and my strength is really mountain biking. I have yet to do a triathlon but have been training on my own for about 1 week. Cycling and running are a bit more natural for me and I don´t feel necessarily deficient in either. I come from the beach in Southern California and have always swam for sports but never for exercise and never efficiently. I can do it but slowly, badly and am the weakest obviously here. I want to do an Olympic triathlon on the 8th of October and am in general good shape but I wonder if I am cutting the training time too short. I´ve been mountain biking 1 1/2 hours every other day for the past year on average and think I´m up the to 40k there and alone I can run the 10k in a little more than an hour without pushing it too much. The most I have ever swam though is only 750m at once. I think I can do it. What do you think? Hopefully I´m not out of my mind...