The Capclave room block has now officially sold out. However, fear not. There are several other reasonably priced hotels very close by including, but not limited to:

Holiday Inn : 2 Montgomery Village Avenue, Gaithersburg, MD
Wyndham Garden Hotel Gaithersburg : 805 Russell Avenue, Gaithersburg, MD
TownePlace Suites Gaithersburg : 212 Perry Parkway, Gaithersburg, MD 20877

Google maps lists a number of other low to moderately priced in the vicinity the above are just the closest.