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Let the cost of one pencil be $a$ and the cost of one pen be $b$. We can set up a system of two equations to represent the given information. The equations are:

$$\begin{array}{rl}5a+b& =2.5\\ a+2b& =1.85\end{array}$$

We are trying to find the value of $2a+b$. Notice that when we add the two equations, we get $6a+3b=4.35$. This is just three times what we are looking for, so dividing both sides of this last equation by three, we get that $2a+b=1.45$. Thus, the cost of two pencils and one pen is $\boxed{1.45}$ dollars.

Alternatively, we could solve our system of equations for $a$ and $b$ and then find the value of $2a+b$. In this case, we get that $a=.35$ and $b=.75$, so $2a+b=1.45$, as expected.