Is it grammatically correct to use もし and/or 〜ば form along with the 〜たい form to convey desire in a conditional clause?


My impression when using conditionals, most of the time, you lose the ability
to express desire. For example, when conjugating to -たら、you have to use the
past tense of the verb. Is it grammatically correct to use もし or ば form to
convey desire in conditional?

> **もし** 公園に行きたいんですが、電話して下さい。

or

> 公園に行きた **ければ** 、電話して下さい。




行きたければ is not past tense. It comes directly form 行きたい.

iku (行く) to go  
iki-masu (行きます) to go  
iki-tai (行きたい) want to go  
iki-takereba (行きたければ) if you want to go

行きたい comes from 行きます by replacing "masu" with "tai".  
行きたければ comes from 行きたい by replacing "i" with "kereba".

You can use もし to reinforce the conditional. The use of もし in this case is
optional.

もし行きたければ  
If you want to go.

There are other ways to express conditionals.  
For example you can use なら:

もし公園に行きたいなら、電話して下さい。

