بسم الله الرحمن الرحيم
If you have to stay in the same area (city or town) for twenty days then you shall be muqim there and it shall be fardh on you to keep fast as you keep at your home.
And if you do not stay in one place (city or town) more than fifteen days and you stay there for less than fifteen days then you shall be musafir there. If you keep fast in view of respect of Ramadan then it is better but if due to the excuse of journey you do not keep it right now, then it is allowed. It is as concession of journey, but it shall be necessary to make its qada later.
Allah knows Best!
Darul Uloom Deoband