Hi,
is there a bus - yup there is on every hour more or less from Estacion Sur. You can check the times and prices via the
ALSA website. If you have a Spanish debit/credit card you can even book online (the last time I tried with a UK card it would not work). A one way trip is about 10-11€.
To get a train you need to get to Chamartin and from there you can take a range of Talgo/InterCity trains or a Regional Express. The price for the latter is about 12€. Again you can check times/prices via the
RENFE website. I believe you can book online Regional trains.
As for la fiestas - they start this thursday with Estopa in (free but no more tickets) concert followed by Ana Torroja, La Oreja de Van Gogh, Chenoa and some others. Just outside the Jose Zorilla Football stadium ( you may have seen it in the news of the cancelled Rolling Stones concert ) the car park is taken up with bars offering food and drink from the different regional associations in Valladolid. If you have never been to Asturias you can go to their bar and pour sidra over yourself, friends and if you are lucky in to your glass.
A full run down of the 10 days of fiesta can be found via
this website.
As towns go - it is ok - night life is very good all year round and is even better for the fiestas. I may be a bit biased since I live there

g